Insights Archive - Hawkins Forensic Investigation

Secant Pile Walls & Basement Excavations: What Could Possibly Go Wrong?

Chloe Duggan — Mon, 08 Jun 2026 08:05:43 +0000

Basements are now routine in urban developments – from plant rooms and car parks to premium residential space. Yet “routine” should not be confused with “simple”. Underground works introduce a unique set of construction risks, which, if not properly managed, can lead to significant issues, increased costs and programme delays. When properly executed, these works enable the construction of challenging basements, even on constrained sites and in areas with high groundwater tables.

Many properties now require basement construction. In most cases, this is achieved using embedded retaining walls, especially in places with limited space with each option. Where groundwater is present, an embedded retaining wall type must be chosen that can retain the groundwater. Sheet pile, secant pile or diaphragm walls are feasible options. CIRIA C760 ‘Guidance on embedded retaining wall design’ provides selection guidance across wall types.

Secant pile walls, in particular, are widely used because they provide support in both temporary and permanent conditions and can be adapted to suit challenging sites. They retain ground and groundwater, minimise ground movement and can carry substantial vertical loads.

Basements may be routine, but they are not simple. Poor planning and/or execution can lead to significant technical issues, cost overruns, and programme delays. Due to their frequent use, this article focuses on secant pile walls – their role, what can be expected of them and the common issues associated with their design and construction.

What is a Secant Pile Wall?

A secant pile wall is a continuous wall formed by interlocking bored piles, as shown in Figure 1.

Primary piles, often referred to as female piles, are installed first, and secondary piles, also known as male piles, are drilled so that each one cuts into the adjacent primaries, creating an interlocking line of concrete. Primary piles are typically unreinforced (see Figure 2).

This system of interlocking primary and secondary piles creates a hard/soft or hard/firm secant wall. The difference between the two wall types is the concrete strength in the primary piles. If the secant wall is used as temporary works only, there is no need for durability or strength requirements for the unreinforced pile, and non-structural concrete may be used. Due to advances in rig power and the cost of using secant walls as temporary works only, hard/soft secant walls have become less common compared with hard/firm secant walls where the primary pile often consists of a low-grade structural concrete, such as a C8/10.

However, in very deep excavations and in response to additional structural requirements, it may be necessary to also reinforce the female piles (see Figure 3). This combination then becomes a hard/hard secant wall which uses high grade structural concrete in both primary and secondary piles.

Secant walls can be constructed using various techniques:

The choice of technique depends on the project requirements, especially permissible tolerances, retained height, depth of interlock required and prevailing ground conditions, see Figure 4. Interlock is the length of wall over which the secondary piles cut into the primary piles. This distance is of particular importance for groundwater exclusion.

Achievable tolerances and typical depth of interlock are defined in the ICE Specification for Embedded Retaining Walls (ICE SPERW) in Table B1.4 and partially reproduced below in Table 1. Whilst the verticality of wall and depth of achievable interlock increase from CFA towards RBP, so does the cost, complexity and the timeframe to install the secant wall.

Advantages of Secant Pile Walls

There are numerous reasons why secant pile walls are often the preferred solution for basement construction:

1. Space Efficiency in Constrained Sites

Urban basements are frequently built tight against property boundaries or adjacent structures. This makes secant walls ideal for city-centre projects where every metre counts.

2. Groundwater Management

Secant walls provide an effective horizontal water barrier when installed correctly. This is particularly valuable where high water tables or sensitive neighbouring assets are present. However, they do not necessarily mitigate vertical groundwater flow into the excavation and should be used in conjunction with a groundwater management strategy (CIRIA C750 ‘Groundwater control: design and practice’).

3. Structural Versatility

Secant walls can serve both as temporary excavation support and as part of the permanent basement structure, reducing duplication of work. They can be designed to carry substantial loads, making them suitable for deep basements and complex load cases.

4. Adaptability

Secant pile walls can be constructed using a variety of piling techniques to address a range of retained heights, tolerance requirements and ground conditions. Secant walls can also adapt to accommodate many footprint shapes. This flexibility makes secant walls a practical choice for many UK ground profiles.

Where Things go Wrong

On paper, secant pile walls look like the perfect solution: strong, versatile, and great for tight sites. But in the real world, things do not always go to plan. Here are the most common issues we see and why they matter.

Misalignement

Secant walls depend on the interlock between primary and secondary piles. However, piles (typically secondary piles) can become misaligned for a variety of reasons, see Figure 5.

Some common root causes for misalignment are given below:

> Primary concrete too hard, causing the secondary pile to deviate into ‘softer’ soil. This is often caused by inadequate or untested concrete mix design and is most commonly seen in CFA walls.

> Incorrect sequencing. Sequencing is of particular importance in CFA secant walls. If the sequence is not planned properly, or disrupted due to site changes or plant breakdowns, the concrete in the primary piles may become too hard, resulting in the defect described above.

> Incorrect technique chosen for interlock requirements. Due to the significant increase in costs from CFA to CCFA and RBP, the interlock limits of CFA are frequently pushed. Joints, especially in standard CFA augers, create a degree of flexibility and make it easier for piles to deviate from the vertical. To minimise this risk, having fewer joints in the auger is better.

> Obstructions in the ground, either natural (such as boulders) or man-made (in the form of old foundations or walls etc.), can cause piles to deviate from their intended position and verticality. RBP techniques are best placed to deal with obstructions in the secant wall alignment and should be chosen if obstructions cannot be removed prior to secant wall construction.

Misaligned piles can affect projects in multiple ways. If the interlock between primary and secondary piles is broken, unwanted soil and water can ingress into the excavation, which will require immediate remedial works (typically through resin injection).

Having sufficient interlock is not only important where it can be seen, i.e. above excavation level, but also below this level to guarantee sufficient water cut-off to make the excavation safe and free of running water. Groundwater entering the excavation from the bottom can destabilise the soil and, in extreme cases, cause uplift failures which should be considered in the geotechnical design of the basement (BS EN 1997-3:2025 – Eurocode 7 – Geotechnical design. Geotechnical structures). To avoid these, the design of the basement should be accompanied by a groundwater management strategy (CIRIA C750 ‘Groundwater control: design and practice’).

In severe cases, a misaligned pile (shown in Figure 5) can impact the spatial requirements of the basement, e.g. the position of liner walls. In these cases, either the out-of-position pile or the secondary element will require structural modification, potentially impacting layouts, available space or structural capacity of the secant wall itself.

Water Ingress

For the avoidance of doubt, secant walls are rarely found to be perfectly watertight. Due to the number of joints between primary and secondary piles, secant walls are vulnerable to water ingress. Damp patches and beads of water (individual droplets of water) are to be expected and do not constitute a defect. The size of damp patches, however, should be less than 4m² per patch, or less than 10% of the visible face of the wall (refer to ICE SPERW 3^rd Edition, Clause B1.9.1 for further details). Weeping water, i.e. where the water runs down the face of the wall, is not acceptable.

Water ingress may occur even if there is no visible sign of misaligned piles. An allowance should be made in the construction programme to permit the piling contractor to deal with leaks through resin injection or other sealing methods.

It is also important to understand that secant walls are classified as Type B protection against water ingress (see BS8102:2022, Table 1) and alone cannot provide a performance level better than Grade 1b (no seepage, damp areas from internal and external sources are tolerable) in accordance with BS8102:2022, Table 2.

Protrusions

Protrusions refer to irregularities on the exposed face of a secant wall after excavation, see Figure 8. Instead of a vertical surface, the wall may have protrusions extending beyond the face of the wall into the excavation. Whilst this is not a structural defect, it can have consequences for follow-on trades and potentially the construction programme.

Protrusions frequently occur in

> Loose natural granular soils or soft clay deposits

> Poorly compacted or poorly graded backfill after obstruction removal (often associated with the removal of an old basement).

> Certain ground conditions where over flighting is a risk associated with CFA techniques (refer to FPS Guidance paper ‘CFA Piling: Preventing ground & rig instability through over-flighting’).

Protrusions in soft/loose/insufficiently compacted ground cannot easily be controlled by the piling contractor. The piling contractor is only responsible for the removal of protrusions in excess of 100mm thickness (ICE SPERW 3^rd Edition, Clause B11.4.2). It is therefore important to allow sufficient time in the construction programme to deal with protrusions, although it is structurally permissible to leave protrusions in place unless they interfere with waterproofing or finishing works.

Concrete Defects

Concrete quality is critical for durability and long-term performance of secant pile walls. Defects can occur during placement and often remain unnoticed until later stages. Using a trialled and tested concrete mix design from established concrete suppliers and undertaking concrete performance testing, are effective ways to minimise the risks of defects. How the concrete is handled on site, for example, avoiding changes to concrete properties through the addition of water, and ensuring the timely and appropriate placing of concrete in accordance with the relevant standards, such as BS EN 1536, ICE SPERW, EFFC Tremie Guide is also of vital importance. Inadequate base cleaning or support fluid exchange, poor tremie practice (RBP only) or concrete supply interruptions can also affect the final product.

Some common concrete defects in secant walls include:

> Shadowing/mattressing, refers to situations where concrete does not flow adequately around the reinforcement bars and leaves ‘shadows’. This defect only occurs in rotary piles.

> Inclusions in piles, which are a common problem and are often the result of inadequate concrete workability. They consist of entrapped materials that differ from the specified concrete and can originate from the surrounding ground (soil or groundwater), poorly cemented material from the original segregated concrete, and may also contain drilling fluids (if used during construction). Inclusions occur more frequently in rotary bored piles as the concrete is placed after the installation of the reinforcement cage and must flow around the bars, but can also occur in CFA or CCFA piles when the concrete has lost its workability.

As a result of inclusions, concrete cover becomes inadequate requiring remedial work. If the inclusions are extensive, they may also provide additional pathways for water ingress (though the reduction of interlock) and may require the down-rating of pile/wall capacity.

What to Expect

Many disagreements occur when expectations between parties are not aligned. The points below summarise what can reasonably be expected:

Secant pile walls are not fully watertight

Secant pile walls manage groundwater inflow, but they do not provide completely dry basements. Damp patches or minor seepage are common and should be anticipated. Flowing water or concentrated leaks, however, are unacceptable and usually indicate defects requiring remedial works. Waterproofing should always follow BS 8102:2022 guidance, with allowances for remedial sealing such as resin injection.

Damp spots do not mean defects

Clients often expect a completely dry basement. In reality, even with a well-built secant wall, some moisture may appear. This is normal and should be addressed through the waterproofing strategy, not treated as a defect.

Overbreak is common

Expect some irregularity on the exposed wall face after excavation. Overbreak often occurs in loose granular deposits, soft clays, or poorly compacted backfill from obstruction removal. Whilst it does not present a structural problem, it complicates waterproofing and finishing works. Extra trimming or patching may be needed, which can affect programme and cost.

Straightness varies by technique

Walls formed using rotary bored piling (RBP) tend to achieve better verticality, greater interlock and straighter faces than those installed with CFA methods. However, while these advanced systems deliver superior alignment, they come at a higher cost.

Consequences for Projects & Claims

When secant pile walls do not perform as expected, the impact is rarely minor. Even small defects can significantly affect the programme and budget. The following outcomes are typical:

Remedial Waterproofing

If water ingress occurs, the leaks are usually treated by polyurethane or acrylate gel injection. This treatment generally stops the leak but can be very disruptive. Injection requires specialist contractors, access to the affected areas, and often multiple visits. Blocking one leak often causes others to appear, meaning costs can increase quickly, and programmes become delayed.

Additional Surface Preparation

Whilst overbreak may be more of a cosmetic problem, it can mean that the wall face is not ready for waterproofing straight away. Trimming, patching, or applying thicker coatings adds time and labour. These tasks are rarely in the original programme, so delays are common.

Structural Downgrades

In rare cases, if tolerances or concrete quality fall short, the wall’s structural capacity may need to be reassessed. This can lead to redesigns, additional props, or strengthening measures, all of which add cost and complexity.

Programme Delays and Cost Overruns

Every remedial step, whether sealing leaks or smoothing surfaces, pushes the schedule out. Waterproofing trades cannot start until the wall is prepared, and follow-on activities like slab casting or fit-out are held up. Claims for delay and disruption are common in these scenarios.

Bottom line: Defects, even cosmetic ones, can have significant commercial consequences. Early planning, engagement with relevant specialists, realistic tolerances, robust quality control, and allowances in programmes are the best approach to avoid subsequent issues.

From our experience, it is essential to follow these steps to minimise issues on site or disputes:

> Define the waterproofing performance grade early (BS 8102:2022) and appoint the waterproofing specialist at the concept stage.

> Select the right wall type for depth, deflection limits and groundwater context (CIRIA C760).

> Make allowances for realistic tolerances (ICE SPERW).

>Plan groundwater management: combine secant cut‑off with dewatering where required; design for uplift; protect adjacent assets (CIRIA C750).

Conclusion: Why Early Attention Matters

Secant walls make complex basements possible, but they are not an “install and forget” solution. Misalignment, protrusions, water ingress, and concrete defects are all common issues that can lead to extra work, cost, and programme delays. Most “problem basements” are not the result of a single catastrophic error – they often stem from a series of small, foreseeable mismatches between design assumptions, construction tolerances, and waterproofing expectations. Addressing those early is far cheaper than dealing with issues later. Standards and guidance exist; the key is to use them proactively.

If you are facing secant wall performance questions, planning a deep basement, or navigating a claim, Hawkins can help – from early risk reviews and design due‑diligence to independent failure analysis and expert evidence. We translate complex geotechnical issues into clear advice and defensible conclusions for clients, contractors and insurers.

About the Author

Yvonne Ainsworth is a Chartered Civil Engineer and Principal Associate at Hawkins, with over 25 years’ experience in geotechnical and structural engineering. Her career includes senior roles delivering complex foundation and retaining wall projects, including secant and diaphragm wall construction on major UK infrastructure schemes. Yvonne is widely recognised for her expertise in piling, ground engineering and resolving high-risk technical challenges, with experience directly relevant to the behaviours, risks and performance of secant pile walls discussed in this article. She brings specialist insight into design, construction methodologies, and failure investigation in complex ground conditions.

References

BS 8102:2022 – Protection of below ground structures against water ingress — Code of practice

BS EN 1536:2010 (+A1:2015)- Execution of special geotechnical works – bored piles

BS EN 1997-3:2025 – Eurocode 7 – Geotechnical design. Geotechnical structures

CIRIA C750 – Groundwater control: design and practice, second edition, 2016

CIRIA C760 – Guidance on embedded retaining wall design, 2017

EFFC Guide to Tremie Concrete for Deep Foundations, 3^rd Edition,2024

FPS Guidance Paper ‘CFA Piling: Preventing ground & rig instability through over-flighting’, 2014

ICE Specification for Piling and Embedded Retaining Walls, 3^rd Edition, 2016

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Keeping the Lights On

Chloe Duggan — Mon, 27 Apr 2026 13:10:45 +0000

The Importance of Fuel Systems in Marine Operations

When combining diesel combustion engines with aeroderivative gas turbines in power generation assets and mechanical drive systems, the fuel specification and adherence to the specification are critical. Compliance ensures the optimal operation, and longevity of the asset and minimises down time.

In marine installations, large vessels can have a mix of propulsion drive systems. Typically, these consist solely of large diesel units, however, in some large vessels, the addition of gas turbines can be found – for that extra bit of thrust/speed.

Both can be susceptible to damage and loss of power if issues exist within the fuel supply system, problems can be caused by using the wrong fuel, or if contaminants are present in the fuel system. If contamination occurs, this can lead to a sudden loss of power which can affect the safety of the vessel. Contamination can compromise the integrity of not only the engine, but also the fuel system, which will require draining and cleaning; both of which will be costly and time consuming to execute. A typical propulsion system schematic is shown in Figure 1. This shows two diesel units and one gas turbine in a two-propeller propulsion system.

If fuel issues arise, both power unit types can be affected. In the example below, I look at how fuel contamination can lead to a buildup of deposits in the fuel system, especially in the final fuel delivery section, which in a gas turbine is the fuel nozzles. The fuel nozzles are complex components that premixes fuel with compressed air and inject the fuel mixture into the combustion can. Combustors see the hottest temperatures.

A schematic diagram of a typical fuel nozzle in a single annular combustor (SAC) is shown in Figure 2. The fuel nozzle is the final link prior to the fuel being atomised into the compressed air flow and ignited.

Issues in the fuel system can be detected by the gas turbine monitoring systems which include temperature and pressure sensors. In SAC gas turbines, there are around 30 fuel nozzles. If issues are developing, the temperature spread around the combustor is likely to change and exceed the permitted temperature spread which is typically limited to approximately 100 to 150°C across eight thermocouples dispersed around the turbine. The fuel pressures in the delivery pipework will also increase as blockages develop. These are both indicators of problems in the fuel supply system, and monitoring of the system’s sensors is of critical importance.

In the case study that follows, excessive temperature spreads and reduced power output were detected over a 72-hour period, indicating an issue with the combustion that required further investigation. This shows how rapid the degradation can be once coking occurs.

Once an issue has been identified, there are limited options for a vessel at sea. The first is to inspect the fuel nozzles to see if there are any visible signs of distress. If deposits are found as in the example below, then all the fuel nozzles will likely need to be replaced. On a gas turbine, each fuel nozzle can cost in excess of 5,000 USD, and a vessel will not carry a spare set on board.

To determine the source of deposits, a laboratory examination of the affected nozzles will be required.

A typical suite of tests includes:

Case Study

Visual examination of the nozzles from the gas turbine that had exhibited excessive T-48 temperature spreads (Figure 3), revealed remnants of liquid fuel, with both the primary and the secondary fuel line blocked by deposits. The primary flow line had been cleared prior to receipt into the laboratory but was reported to be blocked on removal from the gas turbine.

Within the residual fuel, solid deposits were found that were collected and examined. The solid deposits revealed a layered structure (Figure 4) consistent with deposits forming over several operating cycles (stops). This appearance is consistent with coking of the fuel during shut down and thermal soak back. Soak back is the cooling off period after shutdown and can be challenging as it can lead to very high temperatures in the engine damaging equipment back equipment¹. The appearance would also indicate that a purge cycle was not undertaken to remove residual fuel from the fuel line in the area.

The samples collected were analysed using an EDS analyser attached to an SEM. This revealed the deposits to be predominately carbon, however significant traces of sodium (Na) and chlorine (Cl) were detected in areas exhibiting a cubic crystal form (Figure 5). The cubic crystals were observed in all samples examined.

The coking found in the fuel nozzles would indicate that issues were present in the purge sequence of the fuel lines on shut down. In most industrial gas turbine applications, on shut down, the fuel manifold is purged with compressed air to clear the line of residual fuel to minimise the possibility of coking. This did not appear to have occurred. The presence of cubic crystals of sodium chloride indicated contamination of the fuel by ingress of sodium chloride rich solute, such as seawater into the fuel system at some stage.

Besides the issues generated by the coking on the fuel combustion, the gas turbine had been exposed to elevated levels of sodium, which had passed through the high-pressure turbine section. At the temperatures in the hot section of the turbine (high-pressure turbine) this can lead to Type 2 hot corrosion of the turbine blades (which are more expensive than the fuel nozzles). This can lead to a catastrophic failure of the unit if not rectified.

Normally, sodium levels in fuels are specified/restricted to levels down to parts per billion to avoid this degradation mechanism. On the completion of the analysis, it was clear that further investigation was required, into the operating procedures and fuel monitoring during the operation of the vessel.

About the Author

Stephen is a forensic metallurgist with extensive global experience providing independent materials and corrosion advice to multi-national companies within the built environment and engineering industries.

He has over 25 years of experience undertaking failure and root cause analysis for clients in the power, process, and pipeline sectors and has acted as an expert witness across the globe.

¹Predicting engine soak-back with SALAMANDER | Clean (clean-aviation.eu)

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Do I Have a Cladding Dispute?

Chloe Duggan — Mon, 13 Apr 2026 09:45:05 +0000

Over recent years, the safety of a building’s cladding has become a major concern in the UK and the UAE. This is primarily due to the use of combustible cladding materials and ill-fitted or absent fire stopping.

The typical cost of recladding an 18-metre tall building is in the region of £4-5m in both the UK and the UAE. This has led building owners and occupants to consider whether these costs can be recovered from other parties.

Before being able to answer the question, a prospective claimant must first ask ‘do I have unsafe cladding?’. Safety concerns regarding cladding includes structural and fire issues, but this article will focus on non-load bearing facades and therefore fire safety concerns only.

Many of the headlines covering combustible cladding materials initially focused on aluminium composite panels (ACP). However, a building clad in ACP is not the only type of material which could present a risk. There are other cladding types, such as high pressure laminates and external insulated render systems known as EIFS, ETICS or EWI, which may appear to be acceptable but could give rise to a claim.

How do I Know if a Building’s Cladding is Defective?

Defective cladding could be due to the design, construction (installation and workmanship related defects) or both. Design and construction are governed by local building codes, and it is necessary to review a building based upon the codes relevant at the time of design and construction.

In England and Wales, the current relevant codes include the Building Regulations 2010. In the UAE, the current relevant codes include the Fire and Life Safety Code of Practice 2017.

Was the Design Defective?

In England and Wales, there is more than one route to demonstrating compliance with the fire safety requirements of the Building Regulations that the designer/s could have followed:

Linear route: Following the guidance in the Approved Documents, although this does not guarantee compliance with the Regulations.
Performance route: Demonstrating that the performance criteria for external walls in BR 135 have been met by using fire test data from a large-scale BS 8414 test to determine how the proposed façade build-up performs in a fire.
Fire safety engineering route: This would generally follow the recommendations in BS 7974 ‘Application of fire safety engineering principles to the design of buildings – Code of practice’ and take the form of a desktop study that states whether the performance criteria in BR 135 would be met, and as set out later in this article.

Whilst the UAE did not develop its own Fire Life Safety Code until 2011, with the National Fire Protection Association (NFPA) standards being adopted previously, it has been quicker than many other countries to update and introduce more stringent requirements following significant fires.

The review of a design’s compliance with the Code is undertaken by the Civil Defence Authority, although compliance with the code is still the responsibility of the consultant. Any façade system must have been tested and approved by the Civil Defence Authority and the relevant and current approval certificate must be submitted as part of the application for Civil Defence Approval. This, in theory, means that, a design post2011 should not be defective.

However, a building gaining building control or code approval does not necessarily mean that the cladding as designed and installed meets the functional requirements and is not defective.

The most common design defects we have come across at Hawkins include the lack of fire barriers and/or cavity closers. Both of these defects can lead to extensive areas of the external envelope of a building where the spread of fire could be hidden from view. The restricted nature of these cavities can lead to flames that extend up to 10 times the height they would otherwise reach if they were not within a cavity.

The Consultant Told me the System had Been Tested

In the UAE cladding systems must be tested to NFPA 285, which replicates a fire breaking out in the building, spreading through the glazing and igniting the external façade. The test determines the fire performance of an exterior, non-loading bearing wall assembly.

BS 8414, first published in 2002 and some 30 years after the origins of NFPA 285, also provides a test method for determining the fire performance of non-load bearing external cladding systems. The standard is split into two parts; part one tests systems applied to the masonry face of a building, whilst part two tests systems applied to a structural steel frame.

There are a number of issues with statements that a system has been tested to a standard:

Firstly, what was the result? Results for BS 8414 tests are generally not made publicly available, and the BS 8414 test results are not given as a pass or fail (this must be determined by using BR 135). In the UAE, NFPA 285 are available as part of a supplier’s marketing material and without it their products are unlikely to be specified.

Secondly, is the system tested going to be applied in the same way as the test? A masonry applied system will behave differently than a steel frame applied system.

Thirdly, does the system tested match exactly what was proposed for your cladding system? For example: where fire barriers are installed around openings in the test is the insulation the same; and, if it is, is it the same thickness? In one of our cases, it was stated that the EIFS system was tested to BS 8414. The test was relevant for insulation thickness up to 200mm yet the designed system was 320mm in places

The Fire Engineer Said the Design was OK

By following BS 7974, fire engineers can use an analytical process based upon a qualitative design review, in which the possible ways a fire hazard may arise are considered and a range of strategies adopted to ensure that the risk is kept to an acceptable level. This process has a number of stages, including:

A review of the architectural design of the building
Establishment of the fire safety objectives
Identification of fire hazards and the possible consequences
Establishment of trial fire safety designs
Identification of acceptance criteria and methods of analysis
Identification of fire scenarios for analysis
Assessment against criteria.

As you may be able to tell, this is not a quick exercise, and a fire engineer should provide a substantiative reason as to why the guidance in Approved Document B has not been followed, together with supporting evidence to show how the Buildings Regulations are being complied with through another route.

Was the Installation Defective?

What the consultant draws is not always what gets built. Defects we have encountered include lack of fire barriers, intumescent strips to fire barriers impeded so they cannot act as designed during a fire, and incorrectly installed EIFS resulting in cavities between the back of the insulation and the supporting structure.

It is likely that only an intrusive survey will be able to determine if there are defects in the installation. However, an intrusive survey needs to be carried out correctly and those carrying out the survey must understand what they are looking at. In one instance, I have seen a surveyor incorrectly label solid aluminium cladding as ACP, which will have had an effect on the building owner’s insurance premium. In another instance, a surveyor had considered that a lack of cavity barriers in an external wall, indicated that there had been a breach of the Building Regulations, despite the layout of the building meaning there was no other compartment to which a fire could spread.

The above points provide some insight as to whether building owners have a potential route to bring a claim for the costs of remedial works either against consultants, contractors, or possibly both, before a building fire highlights any defects and when it may be too late to ascertain defects in construction.

About the Author

Austen Smith is a Forensic Architect in Hawkins’ Dubai office who specialises in construction defects and defects in architectural design. He has twenty years’ experience in construction projects spanning Europe, the Middle East, the CIS, East Asia and Australia.

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Avoiding a Case of the Blues

Chloe Duggan — Mon, 23 Mar 2026 09:04:41 +0000

Blueberries are a popular ‘superfruit’ with global consumption continuing to increase. In 2023, over 45% of world production was exported. Blueberries can have a shelf-life of up to three months and can be stored below 5°C for up to seven weeks, making them suitable for long-distance transport. However, when a container of blueberries reaches its destination, there could be a ‘case of the blues’ if they have spoilt in transit. In these cases, a forensic investigator can determine where in the supply chain things have gone pear-shaped.

Here Comes The Sun

Optimising a long shelf life starts with good crop husbandry to control pests and diseases. In hot climates, the crop is grown under shade netting, protecting the fruit from sunscald, with polytunnels used to prevent damage by heavy rain or hail in wetter climates. Blueberries should be picked at the 85–90% blue stage in dry conditions in the morning, before heat builds up in the fruit. High humidity at harvest promotes rots and moulds, and berries picked at more than 90% blue stage have a shorter shelf life. Once picked, blueberries should be cooled within five hours as, high temperatures accelerate fruit degradation.

Blueberries are sometimes harvested into crates in the field, but frequent handling removes wax from the skin. This reduces the nutritional quality, accelerates water loss, and speeds decay. To minimise handling, growers are increasingly picking berries directly into branded clamshell retail punnets.

Time to Chill

After harvest, blueberries remain metabolically active, so respiration, ripening and cell aging continue. Upon arrival at the packing facility, the temperature of the berries should be lowered to near 0°C by forced cooling immediately. Temperatures below 2°C for 96 hours kill fruit fly eggs and render mould spores inactive. Care is needed though – while insufficient cooling reduces shelf life, temperatures below 0°C increase chilling injury risk to the berries.

Like many fruits, some blueberry varieties ripen when exposed to the ripening hormone, ethylene. Knowing which variety is being shipped is important, as removing ethylene from storage air can delay their ripening. Ethylene absorbing sachets can help, but add cost.

Happy Atmosphere

Controlled atmosphere transport involves increasing carbon dioxide (CO2) and decreasing oxygen concentrations in an airtight container. Some ‘reefer’ (refrigeration) systems offer a CO2 injection option, allowing containers to be pre-charged to 15% CO2 for blueberries. The auxiliary supply automatically tops up CO2 during transit. However, CO2 supply failure can lead to increased metabolic activity and subsequent fruit breakdown.

Modified atmosphere packaging initially alters the atmosphere inside the pack, but it changes over time. A range of perforated bags are available from manufacturers to wrap entire pallets or individual crates. It is important to use the correct wrapping to avoid losses.

Active packaging changes the condition of the atmosphere to extend shelf-life. Sodium metabisulphite pads release sulphur dioxide (SO2) gas, which kills fungal spores, sanitises small wounds on the fruit surface and maintains the relative humidity within the package at around 89%.

The pads must be placed on top of pallets before wrapping, as SO2 is heavier than air. In addition, the pad must not be allowed to come into direct contact with the blueberries because it is toxic to plant material. Incorrect positioning of these pads can cause mould spoilage or skin bleaching.

Breaking The Mould

More than a dozen moulds can affect blueberries, and an increase in temperature above 2°C stimulates spore germination, initiating irreversible fungal growth, spoiling the shipment. Some moulds, such as Anthracnose (Colletotrichum species) and Grey Mould (Botrytis species) originate in the field due to poor hygiene. Others, such as Blue Mould (Penicillium species), colonise berries during transit due to poor conditions. SO2 primarily controls the mould Botrytis cinerea, a major cause of blueberry spoilage.

Over 300 pests can affect blueberries. One major field pest is the Spotted Wing Fruit Fly (Drosophila suzukii), whilst other fruit fly species colonise the fruit post-harvest. Correct mould or pest identification helps establish liability in the event of a claim.

When The Ship Comes in

Reefer containers maintain the temperature of pre-cooled produce but cannot reduce it further. Pallets should be positioned inside the container to allow for the uniform circulation of cold air. Humidity levels inside the container must also be carefully controlled as too much can promote mould, whereas too little can lead to fruit dehydration and shrivelling.

Take Out Some Insurance On Me

Failing to take the critical steps highlighted above could lead to a ‘case of the blues’ on arrival and an expensive insurance claim.

When faced with a container of spoilt blueberries, it can be daunting for the owner to ascertain how best to understand the root cause and whether the damage is a result of issues during growing, storage or transportation of the crop. A detailed forensic investigation using industry knowledge and expertise in plant diseases can help establish where and why things went wrong and where liability should be attributed.

About The Author

With over 25 years of experience, Plant Pathologist James Townsend has expertise in berries, fresh produce, horticulture and agriculture and is experienced in investigating the causes of plant diseases, crop failures and spoilage of fresh produce. James regularly investigates crop germination failures, crop storage problems, fallen trees, mould contamination, pesticide damage, wildfires and plant disease outbreaks in domestic commercial settings.

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A Structure is Only as Strong as its Weakest Link

Matthew Carrington — Mon, 09 Mar 2026 15:41:10 +0000

Construction projects of all kinds, over a wide range of scale, require structural engineering design input to direct the way they are built. The structural engineering design is almost always implemented in conjunction with architectural design, other specialisms, and the knowledge and skills of the contractor and specialist sub-contractors.

Civil and structural engineering design is a complex field where many engineers are highly qualified, with professional accreditations from engineering institutions after several years of industry experience, following a university degree. However, there is no safeguard against less qualified or less experienced people also trading as civil or structural engineers.

This article discusses the typical aspects of structural engineering design that are required in most construction projects. It includes case studies investigated by Hawkins, where the action of the structural engineering designer could be at fault.

“The strength of a structure depends on the strength of its elements and the way they are joined together.” – Gustave Eiffel

Weak Links

Some building faults might be related to issues with the structural engineering design, or omissions in it. Others may be due to the actions of other parties in the design or construction team, or faulty materials. The design process for each project must consider all the potential modes of failure of the structure. Any one thing could be missed in the design process and cause an issue with the performance of a building. Sometimes, a combination of circumstances needs to coincide to cause a failure. Almost every construction project is a prototype due to the varying combinations of building shape, location and formation of the team performing the work. The following sections describe five links in the structural engineering design chain.

1. Design Issues

It is possible for a structural engineer to completely design the strength and stiffness of the individual elements for the structure but miss a wider issue that can lead to damage or failure.

For example:

The lateral sway stability of part of a building can be reduced by replacing the vertical support from a solid masonry wall with a steel beam;
Loads on a gravity retaining wall at a change of level of external ground that were not allowed for in the design can occur if drainage is not detailed (Figure 2);
Overall structural capacity can be exceeded if a whole category of loading is omitted, such as wind or snow load.

2. Site Issues

There are cases where the design might have considered the typical scenario for the type of structure they designed, but there was something different on site that they did not allow for.

For instance:

If a designer assumed that a wall was a cavity brick/block wall, when it was in fact a solid stone wall, then the wall would be heavier than assumed. A beam installed to create an opening and support the wall could then be overloaded;
A wall that was retaining higher ground could collapse if the rest of the building that was providing lateral support to the wall was removed without considering the interaction (Figure 3);
The effect of a row of small trees on building foundations movement can be greater than the individual trees;
Different ground conditions can have more or less aggressive reactions to the concrete they are in contact with. The wrong mix of concrete might look suitable initially, but in aggressive ground conditions, it can degrade over time.

3. Calculations

Sometimes, the structural designer can miscalculate their designs.

Examples might include:

An assumed length of a beam was not updated in the design calculation when the length of the opening was longer than first planned;
In a structural assessment, the engineer might have used the material properties for normal density concrete when the element was lightweight or aerated concrete, which can only provide lower strengths;
In computer aided design, using finite-element modelling or calculation sheets prepared by a software company, the wrong input for the situation being built can lead to an understrength member. This might arise from one wrong tick in a box within the software options.

4. Stages of Design

There have been cases where the structural engineer provided sufficient design information for a preliminary stage of the design, such as submission to building control, to gain approval for the project to proceed. Then, the client or contractor did not go back to the engineer to ask for detailed design and construction details, or did not correctly apply the submitted preliminary design.

These cases have included:

Where relative positioning between structural members and their supports was critical to the building performance, but the individual member capacity design was sufficient to pass the building control plans check;
Where the order of construction would be critical to the capacity of the structural members. During construction, an unrestrained steel beam would have considerably less capacity to carry vertical loads until it was restrained by the floors to both sides (Figure 4);
Often, changes that appear to make the building simpler to construct can introduce complications to the way they would perform. The changes would need further structural design and could cause a problem if the designer had not been notified.

5. Missing Design

We have investigated cases where an item was overlooked as needing civil or structural engineering design. This can occur at interfaces between specialist contractors’ responsibilities:

i. Roof vents (Figure 5);
ii. Cladding boards (Figure 6).

These will likely perform satisfactorily in normal conditions but might not be sufficient for high winds or rain. This would likely present in the failure of several of the same items. Identifying the fault early might allow the rest of the items to be remediated.

Failures can exhibit a range of states of distress and at different times in the life cycle of a building.

The questions which must be considered when investigating the root cause of the failure will vary with the scenario, including:

Was the designer provided all the necessary and correct information?
Should the designer have found out the correct information by looking into the situation more than relying on drawing or reports they were provided?
Was there information that the designer needed to show in more detail to a competent contractor?
Was there a coordination responsibility to make sure the correct information was provided?
Should a competent contractor have given feedback to the designer that the situation was not as allowed for in the design?
Did the client appointment limit how much the designer could do in any of these aspects?

In some cases, we have been able to advise that urgent action needed to be taken to avoid further damage occurring. This can save people spending time in a position of danger looking for material damage or conducting intrusive investigations that might tip the situation further towards collapse.

“The best design is the simplest one that works”. – Albert Einstein

Conclusions

Sufficient structural engineering design relies on considering all the relevant design issues and all the particular conditions on the site. The structural engineer must complete the design calculations correctly and present the construction information clearly to the contractor. Greater levels of detail are required for the construction issue of the structural drawings than for the building control submission. That is a situation where misunderstandings can arise. Also, there are proprietary and peripheral items related to construction that might not be part of the scope of a structural engineering appointment but would have benefitted from a review by a structural engineer.

How can Hawkins Help?

Hawkins’ Built Environment team can review when something has gone wrong and assess the relevant specialism or party that might have contributed to the issue. Professional experience is important in engineering, including experience of investigation.

About the Author

Jolyon Antill is a Chartered Civil Engineer based in our Reigate office. Graduating with a first-class Master’s Degree in Civil and Structural Engineering, Jolyon has 27 years of design consultancy experience.

His range of industrial and commercial project design work includes new builds, renovations, and structural surveys, both in the UK and overseas. Jolyon also has extensive experience in regional civil and structural engineering consultancies working on educational, residential, leisure and commercial projects. If you have a civil or structural issue and need Jolyon or one of the team to investigate, please contact us.

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Is it Enough to Rely on What The Manufacturer Has Told You?

Matthew Carrington — Mon, 23 Feb 2026 09:51:24 +0000

Construction product manufacturers (‘manufacturers’) frequently provide free continuing professional development (CPD) content. The information is often the first that building designers and other specifiers (‘designers’) receive about a particular product. Designers may then seek further information and advice from manufacturers, including literature, standard details, and specification sections for the selected products, so that they can be incorporated into a project’s technical drawings and specification.

The information received can significantly influence design development and decisions made throughout the procurement process. If a problem arises from a specification incorporating information received from the manufacturer that causes a loss to the designer’s client, the client will most likely hold the designer accountable – not the manufacturer. This is particularly true where a clear contractual relationship exists between the client and the designer, but not between the client and the manufacturer.

Since the Grenfell Tower Fire

Following the Grenfell Tower fire on 14 June 2017, many of the long-standing norms in the construction industry have been scrutinised and found wanting.

In ‘Building a Safer Future‘ published in May 2018, Dame Judith Hackitt highlighted the complexity of construction product testing, labelling, and marketing that designers must navigate, stating that:

“The system that covers product testing, labelling and marketing is at least as complicated as the entire regulatory system […]. It is apparent that the current system makes it difficult to know whether the right products are being used.”

Since 28 June 2022, legal claims can be brought against manufacturers under sections 148^[1] and 149^[2] of Building Safety Act 2022 (‘the Act’). Under section 148, claims may be made where a product has been “installed in, or applied or attached to, a relevant building.”^[3] and it can be demonstrated that the manufacturer took specific actions (including making misleading statements) that resulted in a relevant building being “unfit for habitation”.

Section 146 and Schedule 11^[4] of the Act also states that the “Secretary of State may by regulations make provision in relation to the marketing and supply of construction products in the United Kingdom” called the “construction products regulations”. These may “prohibit the marketing or supply of construction products which are not safe products”.

Following this, in April 2023, the Department of Levelling Up, Housing and Communities published ‘Testing for a Safer Future An Independent Review of the Construction Products Testing Regime’^[5] (‘the Morrell-Day Review’) which made recommendations about how to improve the regulation of construction products.

Since the Grenfell Tower Fire

Statutory duties for designers were introduced in October 2023 when Part 2A of the Building Regulations came into effect. Designers are now required to take “all reasonable steps to ensure the design work carried out by them (and by any workers under their control) is planned, managed and monitored” so that, if built in accordance with that design, the building would comply with all relevant requirements of the Building Regulations.

Phase 2 of the Grenfell Tower Inquiry (‘Phase 2’) further examined construction product testing and marketing and the Phase 2 report, issued on 4 September 2024, recommended that:

“Steps be taken in conjunction with the professional and academic community to develop new test methods that will provide the information needed for such assessments to be carried out reliably”.
“Copies of all test results supporting any certificate issued by the construction regulator be included in the certificate;
“Manufacturers be required to provide the construction regulator with the full testing history of the product or material to which the certificate relates and inform the regulator of any material circumstances that may affect its performance; and
“Manufacturers be required by law to provide on request copies of all test results that support claims about fire performance made for their products.”

The government responded to the Morrell-Day Review and the Phase 2 report by launching a consultation on the “Construction Products Reform Green Paper”^[6] stating:

“Despite the significant reforms initiated in response to the Grenfell Tower tragedy, the government is clear that critical gaps persist in the construction products regulatory framework.”

At the time of writing, the government has signalled its intention to enact further construction product regulations. In the meantime, new testing methods are being developed.

Has a New Relationship Between Designers and Product Manufacturers Emerged?

Some manufacturers will no longer provide technical information without recording project details and caveating the reliance that can be placed on that information. This may include drawing the designer’s attention to the limitations of any tests that the product has undergone, and whether it will be used in an untested configuration.

Yet the designer must still rely on manufacturers’ information to develop designs and select the “right” product for the specific circumstances of each project.

So, What Practical Steps Can be Taken?

Understand What is Required:

Before taking any action, each designer must understand the scope of their design responsibilities relative to others and consider how they will demonstrate compliance with both the standard of care required by their contract with the client^[7] and that required under Part 2A of the Building Regulations. Designers should not assume these responsibilities are the same across all projects, therefore reading and understanding the contract is imperative.

Provide Good Information:

No two projects are the same, and manufacturers can only give advice based on the information they receive. Clearly setting out project-specific criteria helps focus the designer on the principal considerations and enables them to assess which products might be suitable. This information can also serve as a benchmark against which manufacturers’ replies can be compared.

If it Isn’t Clear, Ask:

It is not what the designer believes the information says, but what the information actually says that matters.

If a clear answer is not received, further questions should be raised until the designer is satisfied that a reliable conclusion can be drawn.

Seek Advice From Multiple Sources:

Tempting as it may be to consult only the market-leader, designers should, whenever possible, approach several manufacturers and evaluate each product in context.

Designers must also review the industry guidance and advice that is available at the time of specification and where necessary, seek project-specific advice from independent bodies. The designer should inform the client in writing when further specialist advice is required.

Taking these steps ensures that designers receive a broader range of perspectives and advice upon which to form an opinion.

If a solution limits the choice of material, or if insufficient information is available, the designer should inform the client of the potential implications so that the client understands the risks associated with proceeding, and work collaboratively with the client to explore alternative options.

Certifications, Test Data, and ‘Desktop’ Studies:

In Martlet Homes Limited v Mulalley & Co Limited [2022] EWHC 1813 (TCC), His Honour Judge Stephen Davies reminded designers that a British Board of Agrément (BBA) “certificate is simply one of a number of … specified aids” that “may be used to establish the suitability of use of a material for a specific purpose”, and that the “BBA Certificates cannot be said to amount to a form of “guarantee” or “passport” to compliance with the Building Regulations.”

Designers must establish whether third-party product certification (BBA or equivalent) and product test data are current and applicable to the proposed build-up, and whether additional information is required, such as classification reports from full-scale tests in accordance with BS 8414.

It is often impractical or commercially unviable for manufacturers to undertake full-scale tests for every configuration for external walls; for example, the certification might not exist for the specified build-up. In such cases, an assessment in lieu of tests (AILOTs, ‘desktop assessments’) may be used “to establish by extrapolation how the system being assessed would perform if subjected to the same or a similar test”^[8].

Both Building a Safer Future and the Phase 2 report criticised the use of AILOTs prior to Grenfell. Concerns centred on “the quality of the data available for that purpose and the competence of the person carrying it out”^[9] such that some AILOTs were used to justify materials and components substitutions without sufficient evidence.

The Phase 2 report concluded that AILOTs “should be treated as only part of what is a complex exercise that requires information from various sources.”^[10] Where AILOTs are necessary, they must be “properly evidenced” and based on relevant, existing test data, and undertaken by appropriate accredited bodies e.g. UKAS.

Designers may need to be persistent to be able to demonstrate that they have exercised the standard of care required in obtaining the information needed to make informed decisions. Where information is unavailable, they must carefully assess whether the product is appropriate for use and whether an alternative specification is necessary. Reliance should not be placed on the assumption that a product will pass future testing.

Passing Swiftly From Manufacturer to Designer to Client, Without Passing go:

It can be difficult for designers to verify the accuracy of technical information, and they may lack the competence to scrutinise certain test data. If operating outside their expertise, designers should advise the client and seek support from qualified professionals, such as fire engineers.

Nonetheless, designers should still consider carefully whether the information received passes a ‘fair reading’ and is not ‘an affront to common sense’. They should be able to demonstrate that they reviewed the advice before passing it to others who may reasonably rely on it.

For example, if incorporating a manufacturer’s standard details and specifications into project documentation, designers should review them as if they are its own, since, they may assume legal responsibility for that information. Even if the client instructs the designer to include it, this may not absolve the designer of liability. Limits of responsibility should be clarified in writing at the time of instruction.

Manufacturers’ responses often contain wide-ranging caveats intending to limit their liability. Designers should consider the caveats carefully alongside the technical information received.

Designers should also be cautious of relying solely on their own caveats in their drawings and specifications to limit their liability. Caveats that attempt to unilaterally amend the terms of the designer’s contract with the client may prove ineffective if challenged in court.

Finally – Records, Records, Records:

Records are essential for tracking decision-making and changes throughout the life of a building. Thankfully, most building projects do not end in dispute but when they do, the records kept play a significant role in resolving matters.

The client must only make arrangements for a digital record of ‘golden thread information’^[11] to be retained on higher-risk buildings^[12], not all buildings. Irrespective of literature, notes from meetings with manufacturers, current standards, certification, and other contemporaneous documentation relied upon.

Records are not kept solely for the designer’s benefit, but for those who may need to review them in the future, and understand the detail and reasoning behind the decisions made. Designers should be mindful that product literature changes and manufacturers’ websites are frequently updated, often without clear revision histories. The information they relied upon might not be readily available in the future.

Conclusion

In conclusion, manufacturer information remains a valuable resource, but designers must adopt sound strategies and draw on a range of resources to make informed decisions so that they may demonstrate that they have exercised the standard of care required.

About the Author

Margaret Wright is a qualified architect with first-hand experience of traditional and design and build procurement with novation. She has worked on a wide range of projects including hotels, offices, residential, shopping centres and schools.

As well as identifying risks affecting architects and the wider construction industry, Margaret has provided guidance on a wide range of topics including:

With the introduction of the Building Safety Act, 2022, she has advised on the potential implications of Part 2A of the Building Regulations and PAS 8671.

Margaret has detailed knowledge of the RIBA Professional Services Contracts (PSCs) and architects’ services. She has been a member of the RIBA PSC Editorial Group since 2016, most recently drafting the Building Regulation Principal Designer PSC and the 2024 amendments to Standard, Domestic and CDM Regulation Principal Designer PSCs.

Hawkins can support clients and designers by providing pre-loss risk management advice, and conducting investigations when failures occur. If you think that you may need the services of a forensic architect, please get in touch with us for a free consultation.

References & Footnotes

References:

[1] Section 148 relates to liability relating to construction products.
[2] Section 149 relates to liability for defaults relating to cladding products “attached to, or included in, the external wall of a relevant building”, and applies retrospectively as well as prospectively.
[3] A relevant building is a building that consists of a dwelling or contains two or more dwellings.
[4] Schedule 11 sets out the statutory framework for all construction products.
[5] Authored by Paul Morrell OBE and Anneliese Day KC.
[6] The consultation opened on 26 February 2025 and closed on 21 May 2025.
[7] Foreseeably ‘reasonable skill and care’.
[8] Paragraph 111.50 of the Grenfell Tower Inquiry Phase 2 report.
[9] Paragraph 111.51 of the Grenfell Tower Inquiry Phase 2 report.
[10] Paragraph 111.52 of the Grenfell Tower Inquiry Phase 2 report.
[11] Information about the building required under Regulation 31 of The Building (Higher-Risk Buildings Procedures) (England) Regulations 2023, and which will include the specifications.
[12] Higher-risk buildings are defined in the Higher-Risk Buildings (Descriptions and Supplementary Provisions) Regulations 2023.

Footnotes:
> Building a Safer Future: https://assets.publishing.service.gov.uk/media/5afc50c840f0b622e4844ab4/Building_a_Safer_Future_-_web.pdf
> Building Safety Act 2022: https://www.legislation.gov.uk/ukpga/2022/30/section/148
> Testing for a Safer Future An Independent Review of the Construction Products Testing Regime: https://assets.publishing.service.gov.uk/media/6440f2596dda69000d11e15e/Independent_Review_of_the_Construction_Product_Testing_Regime.pdf
> Construction Products Reform Green Paper: https://www.gov.uk/government/consultations/construction-products-reform-green-paper

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Understanding Chiller System Failures: Causes, Consequences and Prevention Strategies

Chloe Duggan — Mon, 09 Feb 2026 10:00:48 +0000

Chiller systems are a vital component of modern cooling infrastructure, ensuring efficient climate control in various industries, from commercial buildings to data centres. However, when a chiller fails, the financial and operational impact can be substantial. According to a 2022 report from the U.S. Department of Energy, heating, ventilation, and air conditioning (HVAC) failures, including chillers, account for approximately 40% of unscheduled maintenance costs in commercial facilities. Mechanical failures are rarely isolated incidents; they are often symptomatic of underlying inefficiencies that accumulate over time. Proactively identifying and addressing these issues is key to maintaining system performance and reliability. In the sections that follow, we explore some of the common failure points that can compromise chiller system integrity and efficiency.

Compressor Failures: A Silent Threat to System Integrity

The compressor is at the heart of every chiller system, responsible for circulating refrigerant and facilitating heat exchange. According to data published in 2021 by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE), compressor failures account for up to 38% of all chiller system breakdowns. Failures within this component can be attributed to several factors, including overheating, inadequate lubrication, or refrigerant imbalances. Motor burnout, often caused by voltage imbalance or thermal overload, is responsible for over 20% of compressor electrical failures. Early warning signs such as a 10-15% increase in energy consumption or temperature deviations of 2-5°C from setpoints should never be ignored, as they often precede major compressor damage.

Heat Exchanger Degradation: A Hidden Efficiency Loss

Heat exchangers are integral to a chiller’s thermal transfer process, yet their functionality can decline due to corrosion, fouling, and refrigerant leakage. These issues directly impact heat transfer efficiency, forcing the system to operate at higher energy levels to compensate for performance deficiencies. Fouling and scaling can reduce heat exchanger efficiency by 10-30%, depending on the fouling material and thickness. Fouling deposits on heat exchanger surfaces further restrict thermal conductivity, driving up operational costs. A 0.5 mm thick fouling layer can increase energy consumption by up to 20%. While the effects of degradation may not be immediately noticeable, cumulative damage significantly increases the risk of mechanical failure and operating costs over time.

Circulatory Disruptions: Pump & Piping Vulnerabilities

Fluid circulation within a chiller system depends on a network of pumps and pipelines, where even minor disruptions can compromise efficiency. Cavitation, caused by vapor bubble formation, can reduce pump efficiency by up to 40% and significantly shorten pump lifespan. Vapor bubbles can also lead to severe internal damage, while corroded or obstructed piping restricts flow rates, leading to reductions of up to 25% and impacting cooling performance.

The Impact of Refrigerant Leaks on System Performance

A well-maintained refrigerant system is fundamental to chiller efficiency, yet leaks caused by component wear, vibration-induced cracking, or improper installation can severely impact cooling capabilities. Even a 10% reduction in refrigerant charge can diminish heat transfer and lead to a 15% drop in system efficiency. Beyond the financial strain, refrigerant leaks pose environmental concerns and regulatory compliance challenges. Moreover, refrigerant losses significantly contribute to global warming. Hydrofluorocarbon (HFC) based refrigerants have Global Warming Potentials (GWPs) ranging from 1,300 to over 3,900. This means that, over a 100-year period, these gases can trap 1,300 to nearly 4,000 times more heat in the atmosphere than the same amount of carbon dioxide, significantly contributing to climate change.

Operational and Financial Implications of Chiller Breakdowns

The consequences of chiller failures extend beyond equipment replacement costs. Industries reliant on climate-controlled environments face significant operational disruptions. These include healthcare, manufacturing, and data centres, all of which face significant operational disruptions when cooling systems malfunction. For instance, in data centres, cooling system downtime can cost hundreds of thousands to several million USD per day, depending on the size, design, and technology in use. These costs stem not only from the immediate loss of service and potential data corruption, but also from cascading effects on business continuity and regulatory compliance. In high-density environments, where servers generate substantial heat, even a few minutes of cooling failure can cause significant hardware damage.

Unplanned downtime introduces financial liabilities, including emergency maintenance expenses and productivity losses. Furthermore, compromised system components pose safety risks, overheated electrical systems increase fire hazards, while refrigerant leaks present health concerns for occupants.

Expert Analysis: The Role of Mechanical Specialists

Diagnosing chiller failures requires more than just identifying damaged components; it requires a thorough understanding of the root causes behind malfunctions. Mechanical specialists provide invaluable assessments, determining whether failures stem from improper maintenance, design defects, or operational mismanagement. These expert evaluations assist businesses assign liability, whether to manufacturers, installation teams, or maintenance personnel, and also provide actionable insights to improve long-term performance and prevent recurring failures. According to the International Facility Management Association (IFMA), organisations that employ predictive diagnostics experience 30-40% fewer equipment failures compared to those relying solely on reactive maintenance.

Recovery Strategies and Risk Mitigation

A mechanical failure does not always equate to complete financial loss. Businesses may explore recovery options such as insurance claims or legal recourse if system malfunctions can be attributed to negligence or defective equipment. Additionally, implementing predictive monitoring systems can reduce unplanned downtime by up to 50%, enabling businesses to detect performance inefficiencies before they escalate into major failures. Investing in risk mitigation strategies ensures operational resilience while minimising costly disruptions.

Prioritising Proactive Maintenance for Long-Term Reliability

While mechanical failures can result in significant setbacks, preventive maintenance remains the most effective solution for extending chiller lifespan and reducing unexpected breakdowns. Routine inspections, refrigerant system monitoring, and timely repairs all contribute to optimal system performance. Given that chiller systems operate through interdependent components, neglecting any individual element can lead to widespread inefficiencies. Strategic maintenance provides consistent cooling capacity, operational stability, and cost savings over the long term. Well-maintained chillers can last 20–25 years, whereas neglected systems may fail after just 10–12 years. This approach not only maximises cooling capacity and operational stability but also yields annual energy savings of 15-20%.

Conclusion: Prevention Over Repair

Chiller malfunctions can lead to extensive financial and operational consequences, impacting productivity, budgets, and safety. Understanding failure mechanisms and implementing proactive maintenance strategies are essential for ensuring uninterrupted performance. By investing in expert diagnostics and preventive interventions, businesses can safeguard their cooling infrastructure and avoid costly repair scenarios. For chiller systems, early intervention is consistently more cost-effective than reactive repairs.

About the Author

Albert Law is a Chartered Mechanical Engineer and Associate at Hawkins, based in our Hong Kong office. With over a decade of experience in mechanical, electrical, and plumbing (MEP) design and project management, Albert has worked on high-profile projects across Asia and the Middle East, including railway systems, data centres, and commercial buildings. He holds a Master’s degree in Building Services Engineering and is a member of several professional bodies, including the Institution of Mechanical Engineers (IMechE), the Chartered Institution of Building Services Engineers (CIBSE), and the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE). If you have an incident you would like Albert to investigate, please get in touch.

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Water Damage In Basements Part II: Drainage

Lorraine — Tue, 27 Jan 2026 17:03:51 +0000

It is widely reported that climate change will result in an increased flood risk in the UK, with wetter winters and more intense summer thunderstorms. Almost every other year of the last decade saw rainfall records broken and extreme floods affecting various parts of the country.

2024-2025 was no exception: England experienced multiple severe flood events throughout 2024, with major incidents recorded during Storm Henk in January, Storm Kathleen and Storm Pierrick in April, and Storm Bert in late November. These events brought extensive flooding across the Midlands, the south coast, the North East, and parts of the Severn and Trent catchments. During Storm Henk alone, more than 300 flood warnings were issued, affecting areas including Nottinghamshire, Gloucestershire, Worcestershire, and Warwickshire, and causing evacuations, road closures, and widespread property damage.

In April, high spring tides combined with storm surge led to significant flooding along the south coast, including evacuations of over 200 people in West Sussex when the River Arun burst its banks. By late 2024, flood alerts and warnings hit their highest levels since records began, with 7,625 flood alerts and warnings issued across England during the year, a 32% increase compared to 2023.
These “high‑profile” flood events continue to be widely publicised — and for good reason.

Sewer flooding, in contrast, receives little media attention despite affecting thousands of properties a year (generally between 3,000 and 6,000 a year¹). However it can be just as unpleasant, disruptive and costly for those affected – and their insurers.

What is Sewer Flooding, And Why Does it Occur?

Sewer flooding occurs when sewage, often combined with rainwater, backs up from the public sewer and overflows, for example from manholes on the public sewer, or from low-lying sanitary appliances like toilets and showers. There are various reasons why water can back up from public sewers, such as blockages and pump station failures. However, in many cases sewers are simply filled with water due to heavy rainfall.

Perhaps unsurprisingly, properties with living space below ground level, such as basements, are at particular risk. Planning applications cannot fully capture the scale of this issue, as many basement conversions or refurbishments do not require formal planning permission³. However, the Building Regulations will still apply⁴to such refurbishments. ‘Approved Document H’ gives guidance on how to comply with the drainage and waste disposal requirements of the Building Regulations. It acknowledges that public sewers, in particular those that take combined rainwater and sewage, commonly become surcharged, causing a risk of flooding to low-lying properties:

“Combined and rainwater sewers are designed to surcharge (i.e. the water level in the manhole rises above the top of the pipe) in heavy rainfall. Some foul sewers also receive rainwater and therefore surcharge. For low lying sites (where the ground level of the site or the level of the basement is below the ground level at the point where the drainage connects to the public sewer) care should be taken to ensure that the property is not at increased risk of flooding. In all such cases the sewerage undertaker [typically the local water company] should be consulted to determine the extent and possible frequency of the likely surcharge”

How Can Basements be Protected Against Sewer Flooding?

In recognition of the risk of surcharge, Approved Document H requires basements that contain sanitary appliances to have protective measures in order to prevent flooding from the public sewer. It recommends one of two options, depending on the level of risk:

Where there is a low risk of surcharge, and a gravity drainage connection to the public sewer is possible, an anti-flooding valve (also known as a non-return valve) can be used. Anti‑flooding valves should comply with the requirements of BS EN 13564.
Where there is a high risk of surcharge, or if the sanitary appliances are below the level of the public sewer, drainage from the basement should be pumped. Pumping installations should comply with the requirements of BS EN 12056.

The two options are shown in Figure 1. In a pumping installation, wastewater from the basement drains to a sump. When the sump fills up, a float switch activates the pump, which then discharges the collected wastewater into the public sewer via a ‘backflow loop’ (a section of pipe that loops above the maximum expected surcharge level). During times when the public sewer becomes surcharged, the backflow loop prevents water from the public sewer from backing up into, and overflowing from, the sanitary appliances in the basement. Meanwhile, the pump continues to discharge wastewater from the basement.

Various safety measures can be provided to manage the residual risk of flooding should the pump become overwhelmed or fail; for example backup/standby pumps, auxiliary power supplies, alarms and telemetered alerts that warn of a high water level in the sump.

Anti-flooding valves can range from simple hinged flaps that open and close with the weight of the water, to more complex motorised flaps that are triggered by pressure sensors, however their principle of operation is the same. They are designed to be open when the water level in the public sewer is low, allowing wastewater from sanitary appliances in the basement to discharge by gravity. Therefore anti-flooding valves are only suitable where the sewer is below the level of the basement’s drains. When the public sewer becomes surcharged, the valve is designed to close automatically to prevent water backing up and flooding the basement.

Another key requirement of Approved Document H is that “all drainage unaffected by surcharge [for example sanitary appliances above ground level] should by-pass the protective measures and discharge by gravity”. This is important to limit the amount of wastewater that can become ‘trapped’ upstream of an anti-flooding valve while it is closed (or upstream of a pump, should it fail).

What Can go Wrong?

Pumping installations can fail for a variety of reasons. Some common examples include:

> The failure of the float switch to activate the pump if it is unable to move freely. This can result from a lack of maintenance, or if the pump and float have been installed in a sump chamber that is too small. High level alarms are generally operated by a float switch, and so can fail in a similar way.

> Mechanical failure of the pump, possibly due to gradual wear and tear.

> Electrical failure of the entire installation, if the primary pump is installed on the same circuit as the safety measures, such as backup pumps and alarms (which we have seen on numerous occasions). An electrical fault on any one component can cause the whole installation to fail.

> Failure of the pipework downstream of the pump can prevent the pump from discharging water from the sump.

Both pumping installations and anti-flooding valves require regular inspection, testing and maintenance. The recommended frequency is generally specified by the manufacturer and/or other relevant guidance (for example BS EN 12056 and BS EN 13564).

A lack of maintenance can result in an anti-flooding valve’s movement being impeded and can restrict its ability to form a watertight seal.

If an anti-flooding valve does close effectively, preventing backflow from the public sewer, wastewater cannot discharge from the basement. The trapped wastewater creates a risk of flooding in its own right, and is why anti-flooding valves are only recommended when there is a low risk of surcharge. A person in the basement would probably notice that water was not draining from their sanitary appliances, and would most likely stop using them before flooding occurred. However, if sanitary appliances (or rainwater) from above ground level have been connected upstream of the anti-flooding valve (contrary to the requirements of the Building Regulations), the people using those appliances are unlikely to realise that their wastewater is becoming trapped in the basement drains until it is too late.

Care is also required when making alterations to either the drains or the sanitary appliances in the basement. For example, the installation of a shower in the basement can increase the risk of flooding by providing a lower point from which the drainage system can overflow (as opposed to an item positioned off the floor, like a sink).

Potential Routes For Recovery

As with many other types of losses, recent building work should always raise a ‘red flag’ for subrogated recovery. Even minor works (such as installing a shower) or works that might seem at first to be remote and unrelated (for example alterations to the drainage of upper storeys) can be worth considering. Some common third parties who might have contributed to a sewer flooding incident include:

> The architect / designer. Was the drainage system designed appropriately and in accordance with the relevant regulations and standards? Was the water company consulted and were the appropriate protective measures specified?

> The installation contractor. Were the drainage system and protective measures installed in accordance with both the design and the manufacturer’s specifications?

> The maintenance contractor. Were the protective measures maintained in accordance with both the relevant standards and manufacturer’s specifications?

It can also be worth investigating why the public sewer became surcharged. For example, there may be a potential for recovery if a public sewer became either damaged or blocked by a third party contractor working in the road.

Our experts have many years of experience investigating and identifying the causes of flooding and drainage failures, and advising on measures to reduce future risk. If you are interested in hearing more, please contact us. You are always welcome to call one of our experts for an informal, confidential chat with no commitment.

About The Author

Richard Keightley is a Chartered Water and Environmental Manager and Chartered Environmentalist. He specialises in the investigation of flooding, water ingress and drainage issues, and has provided CPR-35 expert witness evidence in civil claims for both claimants and defendants. Richard joined Hawkins in 2017 as part of our civil engineering team, having previously worked at two major engineering consultancies, a water and sewerage company and New Zealand’s National Institute of Water and Atmospheric research

[1] https://discoverwater.co.uk/sewer-flooding

[2] https://www.directlinegroup.co.uk/en/news/brand-news/2017/british-property-market-goes-through-the-floor.html

[3] https://www.planningportal.co.uk/info/200130/common_projects/5/basements

[4] https://www.planningportal.co.uk/info/200130/common_projects/5/basements/2

National assessment of flood and coastal erosion risk in England 2024 – GOV.UK

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The Explosive Risk of Additive Manufacturing

Chloe Duggan — Mon, 12 Jan 2026 09:09:04 +0000

As a fire investigator with Hawkins who has previously worked on developing Additive Manufacturing (AM) technologies in research and in the medical device industry, I am particularly interested in dust explosions linked to AM. In this article, I will explore the risk of dust explosions in the AM environment and the current best practices for preventing them.

What Are Dust Explosions?

So, what is a dust explosion? Mr Rolf K Eckhoff states in his book “Dust Explosions in the Process Industries” that “any solid material that can burn in air will do so with a violence and speed that increases with increasing degree of sub-division of the material.” ¹ As we all intrinsically know, if we are trying to start a fire in an open hearth or stove, we make kindling first, breaking a large piece of wood into smaller pieces rather than attempting to ignite a large log. By making kindling, we increase the surface area of the wood, increasing the degree of sub-division of the wood, enhancing the speed of combustion and reducing the energy requirement for ignition.

A dust explosion can be defined as the rapid combustion of fine particles suspended in the air, often in an enclosed location. This type of explosion can occur when a dust cloud (an assembly of dust particles suspended in air) of the right concentration is exposed to an ignition source, such as a spark or flame. The “right” concentration here refers to somewhere between the upper and lower limit of the ratio between dust and air within the cloud that will support combustion, more on this later.

In conventional fire investigation, we use the basic principle of the fire triangle, a simple model for understanding the necessary ingredients for all fires. It consists of three elements: heat (ignition source), fuel, and oxygen. For a fire to ignite and sustain itself, all three components must be present. For dust explosions, this triangle is extended to a pentagon to include the dispersion of dust particles (a dust cloud) and confinement. For a dust explosion to occur, all five elements of this pentagon need to be present. Thus, similarly to our fire triangle, removing any one of these elements can prevent a dust explosion.

The term “ATEX” comes from the French “ATmosphères EXplosibles.” An ATEX environment refers to a workplace where there is a risk of explosive atmospheres due to the presence of flammable gases, vapours, or combustible dust mixed with air. For some AM technologies, particularly those using powder as a raw material, the manufacturing floor is considered an ATEX environment.

What then is a combustible dust? Let’s take a small step back. Dust explosions in general arise from a rapid release of heat produced during the chemical reaction of combustion:

fuel + oxygen = oxides + heat

This means that only combustible materials, ones that are not already stable oxides, can form dust clouds capable of explosion. As a result, clouds of cement or fine sand will not give rise to a dust explosion. If this wasn’t the case, sand storms would be a lot scarier. On the other hand, materials that can give rise to dust explosions include natural organic materials such as grain or sugar, synthetic organic material such as plastics, and even metals such as aluminium, magnesium or titanium. When in a fine particle form, these materials are referred to as combustible dust.

Examples of Dust Explosions

There are myriad examples of dust explosions throughout history involving diverse types of combustible dust and different ignition sources. One example involving the production of metallic powder was at an atomised aluminium powder production plant in Anglesey in 1983. Mr Rolf K Eckhoff’s book “Dust Explosions in the Process Industries” describes the explosion as having swept through the entire plant. Neither the ignition source nor the point of ignition was determined. However, the extensive damage highlights the risk of dust explosions and the progression of the explosion from its point of ignition to the rest of the plant highlights the importance of managing intentional or unintentional dust accumulations in the manufacturing environment.

A more recent incident involving metallic powder happened at a Woburn Massachusetts AM company on the 5th November 2013. A news release from the U.S. Department of Labour stated that the company failed to protect its workforce from the hazards of combustible metal powders like titanium and aluminium alloys.

Key issues included;

Additive Manufacturing

The case study allows me a convenient time to introduce AM. So, what is it?

Since its inception in 1981 by Dr Kodama of the Nagoya Municipal Industrial Research Institute, many terms have been used to describe the process of creating a three-dimensional object directly from a numerical model by stacking two-dimensional layers. The most prevalent terms, in chronological order, are rapid prototyping, 3D printing, and additive manufacturing (AM). Observing these terms in sequence provides insight into the technology’s development over the past four decades, evolving from a prototyping tool to a fully-fledged manufacturing process.

AM has been at the forefront of innovation in various industries. It has revolutionised the aerospace sector by enabling the creation of components with intricate and organic shapes that were previously difficult or impossible to produce using traditional methods. This technology allows engineers to design components by placing material only where stress acts, thus allowing for more efficient use of material and making parts lighter, which is crucial for improving fuel efficiency and reducing emissions in air travel.

In the medical device industry, AM has facilitated advances in patient-specific implants, prosthetics, and surgical guides, where the device matches the patient’s specific anatomy. AM has also been used to create unique geometries that enhance the clinical benefits of devices, such as orthopaedic implants composed of fine lattices that promote osteointegration.

AM has undergone significant development since its initial use for prototyping. It has evolved into a multi-material, multi-scale manufacturing technology with numerous subsets.

These subsets, although all categorised as AM, differ in the mechanisms by which they create the two-dimensional layers, this can be done in the following ways;

Extrude molten thermoplastic from a heated nozzle
Use light, in the form of lasers or projections, to solidify liquid polymer resins
Deposit adhesives onto metal, polymer, or ceramic powders, creating a green body that must be sintered
Melting powders by direct exposure to a laser, which, when resolidified, creates a solid mass of material

The raw material input for AM processes varies and can generally be categorised as filaments, resins, or powders. This article will focus on powders, with a particular interest in managing these powders to ensure safe use.

Risk and Prevention

Now that we understand the basics, let us consider the risks of working in an ATEX environment on an AM manufacturing floor that utilises metallic powder as its raw material. The raw material, the powder, is loaded into the 3D printing system, either manually or automatically. This powder is often recycled from previous printing processes so may have already gone through a sieving process, or other pre-printing processes to ensure its suitability for use. Printing occurs and the parts are removed from the powder cake i.e. the mass of powder held within the printer that contains the printed parts. Part removal is often manual and involves extraction of unused powder. After printing, parts go onto secondary processes where they are further refined and unused powder is recycled further. I paint this simple picture of a common AM process to illustrate how much powder is handled during the printing process in an attempt to describe how difficult it is to contain this powder. Powder inevitably escapes the confinement of the various processes and enters the manufacturing environment where it builds up on surfaces and is extracted through air handling systems.

Let me pause this quickly and introduce the concept of primary and secondary explosions. Dust explosions cannot occur unless the dust concentration within a cloud is within certain limits. Too much dust in a cloud and combustion will not occur due to lack of oxygen, too little dust in a cloud and combustion won’t occur due to lack of fuel. If we imagine disturbing a small pile of dust, this will rise and start to spread out in the surrounding air before settling back onto nearby surfaces. At some point between dispersion and resettlement, the concentration of dust may be suitable for dust explosions. This illustrates the danger of disturbing accumulated dust. This is important to understand this mechanism as we consider primary and secondary explosions. An initial dust explosion can disturb accumulated dust and generate a secondary dust cloud that can lead to secondary explosions. Depending on the volume of accumulated dust that is disturbed, this secondary explosion can be more severe than the primary.

So how do we prevent risks of both primary and secondary explosions in an AM environment? Let’s reference back to the dust explosion pentagon and recall that if we remove one corner of the pentagon, a dust explosion will not occur.

Oxygen 

Oxygen is often removed locally at the AM process, selective laser sintering for example is often conducted under a forced argon environment. However, for obvious reasons, it is not practical or safe to remove oxygen from the wider manufacturing environment.

Ignition sources 

In a well-managed environment, ignition sources most commonly come in the form of a spark, either from mechanical impact possibly during tool use or from machinery, or the discharge of electricity, possibly an electric fault or from the build-up and discharge of static electricity. However, they can come from any sufficient source of heat such as an open flame, from welding or grinding of metals, or from hot surfaces such as poorly maintained and overheated bearings. The probability of a spark from mechanical impact or an electric arc can be reduced through the use of ATEX-rated equipment, tools, and machinery. Earthing all equipment, installations and even personnel through specific PPE can reduce the build-up of static electricity and thus reduce the probability of electric discharge. Equipment must be well maintained to reduce the probability of malfunction leading to hot surfaces or electric faults.

Fuel 

In general, the fuel is the powder material that is the input into the AM process. Thus, it is not possible to remove this element entirely. However, some materials are more combustible than others, so, when possible, a less volatile material should be selected. Additionally, regular cleaning and maintenance supported by sufficient air extraction can reduce the available fuel in an environment.

Dispersion 

Similarly to fuel, cleaning and maintenance supported by a sufficient air handling and extraction system will remove the fuel from the environment, reducing the risk of dispersion.

Containment

The removal of containment from the pentagon is not practically possible. This would involve running the manufacturing process outdoors. Furthermore, reducing containment by placing the manufacturing process in a large open-plan space would be difficult too, as the whole space would be subject to the same stringent cleaning and maintenance, as well as the same equipment and ways of working protocols suitable for an ATEX environment.

In review, the most practical way of reducing the risk of a dust explosion in an AM environment is to reduce the likelihood of ignition and, in parallel, reduce the build-up of fuel in the environment.

Relevant Standards and Regulations

ISO/ASTM 52931, titled “Additive manufacturing of metals — Environment, health and safety – General principles for use of metallic materials,” addresses fire and explosion risks in AM environments using metallic powder. It mandates avoiding all ignition sources, including static discharge, hot surfaces, open flames, and live circuitry. Measures to limit static discharge include using grounded antistatic equipment, surfaces, floors, garments, and grounding personnel. Controls must prevent powder from escaping the AM system, with air handling systems capturing powder and minimising atmospheric exposure, and workspaces designed for cleanability.

The Health and Safety Authority of Ireland’s “Guide to the Safety, Health and Welfare at Work (General Application) Regulations 2007 Part 8: Explosive Atmospheres at Places of Work” ² requires employers to take technical and organisational measures to prevent explosive atmospheres or avoid ignition, including electrostatic discharges.

Both documents conclude that to reduce dust explosion risks, all ignition sources must be removed, and dust must be contained and minimised to stay below the lower limit of concentration. This is the same conclusion we arrived on after our interrogation of the pentagon.

Risk of Maintenance

Regular maintenance and well-considered work practices are key to mitigating against dust explosions. However, as discussed by my colleague Mr Nick Ashby in his recent insight article “The Perils of Maintenance,” it is often during maintenance, especially unplanned, that many accidents occur. Stepping away from the day-to-day ways of working to conduct maintenance can lead to an increased risk of dust explosions. Dust that may have been hidden from cleaners can be disturbed when equipment is moved, increasing the fuel load in the atmosphere. Furthermore, the use of tools that aren’t designed for an ATEX environment; conventional hammers may produce a spark when struck off a hard surface, however, specialised bronze-headed hammers will not. A more obvious ignition source is introduced if hot works are required. Nonetheless, not conducting maintenance also increases risk. Thus, the perilous task of maintenance must be conducted, but also de-risked through well-considered risk assessments and ways of working that fully consider the unique requirements of an ATEX environment.

Conclusion

In conclusion, while AM technology offers numerous benefits, it also presents additional risks such as dust explosions. Adhering to safety standards, conducting regular maintenance, and ensuring fully trained workers are essential to mitigating these risks and balancing innovation and safety in the exciting world of AM.

About The Author

Jason joined Hawkins in April 2024, he has lead fire investigations in domestic, industrial, and commercial environments. Jason is an accomplished Materials Engineer with a strong background in Additive Manufacturing. He graduated with First Class Honours and conducted research on optimising projection stereolithography additive manufacturing, focusing on the relationships between process parameters, material structure, and mechanical properties. Jason has experience supporting production and optimising manufacturing processes, including laser welding, cutting, and marking. His expertise extends to developing (Eckhoff, 1997) additive manufacturing processes for medical implants and instruments, working with materials like PEEK, nylon, and titanium.

Eckhoff, R. K. (1997). Dust explosions in the process industries. Reed Educational and Professional Publishing Ltd.

Occupational Safety & Health Administration. (2014, May 20). OSHA News Release: After explosion, US Department of Labor’s OSHA cites 3-D printing firm for exposing workers to combustible metal powder, electrical hazards [05/20/2014].

Retrieved from https://www.dol.gov/newsroom/releases/osha/osha20140520-2

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Bye Bye Bamboo: Why Hong Kong is Phasing Out Traditional Scaffolding

Matthew Carrington — Mon, 24 Nov 2025 10:56:48 +0000

Bamboo scaffolding, alongside neon signs and red taxis, has long been a defining feature of Hong Kong’s urban landscape. But like many cultural icons, it is now facing a quiet retreat. In a move driven by safety concerns, The Government of Hong Kong is beginning to phase out bamboo scaffolding in public construction projects, marking a significant shift in the city’s construction practices.

A Policy Pivot Toward Metal

On the 17 March 2025, the Development Bureau of Hong Kong issued a circular memo titled “Adopting of Metal Scaffolds in Public Works”. This document outlines a new requirement that from 21 March 2025, all public works tenders must specify the use of metal scaffolding. Bamboo may only be used in exceptional cases, and only with detailed justification.

The Bureau cited bamboo’s “intrinsic weaknesses,” including inconsistent mechanical properties, susceptibility to deterioration, and high combustibility, as key reasons for the change. Additionally, the Bureau is cognisant of the wide adoption of metal scaffolding in Mainland China and other advanced economies.

The Case for Bamboo

Despite its drawbacks, Hong Kong has historically favoured bamboo scaffolding for several compelling reasons. It is:

These advantages have contributed to bamboo scaffolding becoming a staple of the city’s construction industry for decades. However, safety concerns have persisted.

Putlogs: A Common Source of Failure

A 2004 study by Tsinghua University titled “Comparative Study of Safety and Application of Bamboo and Metal Scaffolding in Hong Kong”^[1]found that the most significant hazard in both systems was the failure or absence of putlogs – horizontal members that tie scaffolding to the building structure. An excerpt from the paper showing the hazards associated with both types of scaffolding can be seen below.

Interestingly, Hong Kong’s safety codes impose stricter requirements on bamboo scaffolding putlogs than on metal ones. Bamboo scaffolds (under 100m in height from ground) must have putlog ties spaced no more than 3 meters horizontally and 6.3 meters vertically (equivalent to one per 18.9m²), with each tie capable of withstanding 7kN^[2]. In contrast, metal scaffolds require only one tie per 25m², with a lower strength threshold of 6.25kN^[3].

This raises a critical question: if bamboo scaffolding is held to higher standards with regards to putlogs, why is it perceived as less safe?

The Real Risk: Lack of Oversight

A recent scaffolding collapse involving 20 workers revealed the true issue: inadequate professional oversight. Investigators found that the metal ties used for the bamboo putlogs were as thin as 1.06mm – far below the required 6.00mm^[4]. The collapse was not due to the use of bamboo itself, but to unauthorised modifications and a lack of professional design and supervision. A government safety officer emphasised the need for scaffolding to be professionally designed and approved. The Chairman of the Construction Industry Council echoed this, calling for better coordination among engineers, supervisors, and qualified personnel to prevent such failures^[4].

Looking Ahead: A Role for Expertise

While the shift to metal scaffolding may reduce some material-related risks, it does not reduce the need for professional oversight. Whether bamboo or metal, scaffolding systems must be properly designed, installed, and maintained.

The phasing out of bamboo scaffolding in public works marks the end of an era in Hong Kong’s construction history. Although the decision is rooted in legitimate material safety concerns, it also reflects a broader shift toward modernisation and regulatory rigour. As this transition unfolds, it is essential to recognise that safety is not solely a matter of materials and regulations – it is also a matter of professional expertise.

How can Hawkins Help?

At Hawkins, our chartered civil and structural engineers bring deep industry experience in design consultancy, site supervision, and forensic investigation. We offer guidance to the construction industry, helping define and develop working procedures and practices that reduce the risk of incidents and lead to safer outcomes. Our Hong Kong team has investigated a wide range of incidents, including, crane and material hoist collapses, concrete spalling, slope failures, and structural damage from vehicle collisions. Our goal is to provide clarity, accountability, and actionable insights that help prevent future incidences.

About the Author

Patrick is a Chartered Structural Engineer based in our Hong Kong office. He has many years of experience in the construction industry and has worked for both contractors and consultants on temporary and permanent structural works. He has designed temporary supporting structures for both metal and bamboo scaffolds. As a resident site engineer, he has also monitored scaffold construction safety and ensured that temporary working platforms are adequate to support all intended loads.

Patrick joined Hawkins as an associate in 2024 to expand the forensic structural engineering capabilities of Hawkins in the Greater China and Asia region.

If you would like to discuss any incident—whether related to the built environment or any of the many other scientific and engineering disciplines Hawkins supports its clients with worldwide, please get in touch.

References:

[1] Fang, DP, Wu, SH, Wong, KW & Shen, Q 2004, A comparative study on safety use of bamboo and metal scaffolding in Hong Kong. in Construction safety management systems. Spon Press, pp. 373-386.

[2] Hong Kong Labour Department 2024, Code of Practice for Bamboo Scaffolding Safety, Fifth Edition.

[3] Hong Kong Labour Department 2013, Code of Practice for Metal Scaffolding Safety, Second Edition.

[4] Hong Kong Construction Industry Council 13 February 2025, Life First Walk the Talk Webinar – Bamboo Scaffolding Safety and Code of Practice.

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