A building owners’ guide to flammable cladding

As a building owner you’re more than likely familiar with the Grenfell Tower fire of June 14, 2017. But could it happen to your building?

This article follows the current common practice used in cladding evaluations from start to finish with the intent to better inform building owners of the process, reasons behind each step, what they can expect as an outcome and their statutory responsibilities.

What types of cladding are there on my building? Is it flammable? How much is there? Is it safe to leave? What are my legal obligations? Are there any options other than having to remove it? Will the replacement look and perform the same?

These and many other questions have been confronting property owners and facility managers over the past couple of years, with the Grenfell fire bringing the issue into particularly sharp focus. Without a technical background, understanding even where to start can be daunting, especially when the outcome of such a process could become an expensive burden on the asset owner.

 

Your responsibility

The presence of flammable cladding on your building is not just an abstract concept. Over 90 deaths have been directly attributed to external combustible cladding fires over the last decade.

The division of responsibility between designers, architects, builders, contractors and owners is not the same for new and existing builds, nor is it uniform from state to state.

In Australia, the builder of the 21-storey Lacrosse Apartments in Victoria experienced a near fatal fire in November 2014 and will likely pay the approximately $AUD16 million in costs to replace the cladding. However, the liability for ensuring the safety of a building and its occupants is falling increasingly to the owner. Owners of the Anstey Apartments in Brunswick, Victoria have been ordered to replace the cladding on their building, at an estimated cost of two to three million dollars.

An added complication for owners is that buildings that do not comply with regional statutory requirements are unlikely to be covered or compensated by insurance.

What is ‘ACP’?

The common culprit in incidents such as Grenfell and the Torch Tower in Dubai is Aluminium Composite Panels (ACP) and it is this cladding type that is receiving the bulk of attention with regard to industry action and current policy creation.

These panels are four to six millimetres thick with a 0.5 millimetre thick aluminium skin on both faces. The central core is typically polyethylene-based, but can also be bakelite or other plastics. Polyethylene (PE) is derived from oil and is highly combustible. It constitutes the ‘organic’ component of the core. There are fire retarding (FR) varieties where a significant proportion of the organic material is substituted with a chemical which is meant to actively combat the advancement of the fire. These are called ‘inorganic fillers’ or ‘mineral fillers’ in some industry documents.

ATH (aluminium trihydrate) and to a lesser extent MDH (magnesium hydroxide), are by far the most common inorganic fillers used in panels found in Australia. These are ‘active’ fillers which actively work by releasing the hydrate of the filler as steam when combusting, thus ‘sucking’ energy out of the fire and hopefully extinguishing it. ‘Inert’ or ‘passive’ fillers such as oxides are also possible. These work by simply being non-combustible but do not actively retard the combustion process. Very often, a panel will have both inert and active constituents because commercial FR agents are rarely 100 percent pure.

What counts as ‘FR’?

A lot of confusion arises around the definition of what counts as ‘fire retarding’. Generally, commercial FR products have passed a combustibility test such as European Standard EN13501-1 and a large-scale fire test such as the US NFPA 285 or British BS 8414. Such products typically contain more than 70 percent ATH (or greater than 55 percent MDH). These are not magic numbers, nor are they to be found in any technical standard. This is just the minimum required percentage that manufacturers have found to reliably pass the test requirements.

When assessing existing buildings, it is impractical and uneconomical to execute a full-scale test on panel samples. Therefore, ‘proxy’ assessments are used based on the chemical composition of the core (verified by laboratory testing). That is, if the panel sampled contains 70 percent ATH or more, then it is assumed it would perform similarly in a full scale test to a branded product with an existing certification and a similar mineral loading.

The problem with this approach is that there are manufacturing tolerances in real panels as well as the measurement errors inherent in the lab testing, so the outcome is that filler levels at or above 70 percent (for ATH panels) may only be true half of the time. Some authorities, such as the Insurance Council of Australia, quote lesser levels (e.g: 65 percent ATH) to compensate for this variability and avoid excessive rejection of existing installations.

BRE (building research establishment) testing has shown that even if the panel is compliant, the entire wall build-up (cladding, insulation, sarking/backpan and internal lining) may still fail a fire safety engineering assessment if one or more of these additional layers are combustible. In Australia, the new Standard AS 5113 requires that the full wall build-up be fire tested to ensure non-combustibility of all components. As such, we should be considering all elements in the wall.

Step one: inspection

The first step on the road to securing your building is getting it inspected. An inspection will involve review of the building documentation: ‘as-built’ drawings, facade maintenance, manual and warranties, any fire safety engineering reports and annual fire safety statements. The extent and location of the cladding, the presence of fire mitigation measures (e.g. sprinklers) and risks (e.g. ignition sources and proximity to fire escapes) are also recorded.

Next will be a physical inspection of the building to confirm and identify the cladding present. While helpful, documentation is not always correct. Any ACP identified should be further investigated to ascertain its core type and, if possible, its provenance. Broadly speaking, there are two ways to do this – removal of a panel (one panel per different cladding type identified) to reveal the manufacturing details printed on its rear surface, or retrieval of small samples for lab testing.

Removal of panels can be expensive, laborious and, if no labelling exists on the back of the panel, unfruitful.

The second route is more straightforward and easier to budget for. Samples of each identified type of cladding are retrieved for lab testing – usually as one-inch cores made with a hole saw. Samples of any insulation and sarking associated with the cladding system should also be taken, and the particulars of the panel fixing arrangement, treatment of the exposed core (exposed or folded edges) and so on are recorded. Endoscopic cameras may help in this respect.

Step two: testing

In cases where removal of panels has been carried out and was fruitful in that manufacturing details have been identified, testing may not be required. In all other cases, the second step is testing of retrieved samples.

The rest of this article focuses on our in-house methodology and other parties may have slight variations in their approach. Regardless of who is carrying out the testing, all testing procedures should aim to identify the nature and percentages of the filler and polymer components.

There are three types of testing: density, flame testing and lab testing, which are described below.

Density testing is often useful to confirm a visual identification because the density of a material is a fixed physical property. For example, true ATH fire retarding cores can never be less than ~1.6 times the density of polyethylene (LDPE) ones. This is a function of the higher density of the mineral relative to the polymer and the loading of the mineral relative to the polymer.

Physical properties like visual appearance are often a good indicator of the core type. Jet-black homogenous surfaces are usually indicative of polyethylene. White or grey cores with an obvious gritty (heterogenous) appearance are typically associated with fire retardant cores. However we have found that in about 10 percent of cases, core colour bears no association to the actual core type.

The second test type is flame testing. Applying a flame to the internal core of the panel will give a fast qualitative indication of the core type. Phenolic cores will char and not melt. Polyethylene cores will ignite rapidly and burn even after removal of the flame, often with flaming droplets. Fire retardant (FR) polyethylene on the other hand, will ignite with difficulty, then swell and foam for as long as the flame is applied. They will usually self-extinguish within a few seconds of the flame removal.

The third form of testing is laboratory characterisation, which is needed to confirm the core type and its chemical make-up. We have found that a panel of three tests provides the information needed to accurately identify the types and percentages of the core components with a high degree of confidence. That is, Infrared spectroscopy (FTIR) can reliably confirm both the type of polymer and inorganic filler. Ashing (where the sample is burnt and the remaining inorganic matter weighed) reliably informs us of the percentage (w/w%) of plastic in the sample, while X-ray fluorescence (XRF) gives us an accurate value of the proportions of each of the different inorganic minerals in the core. Other tests in use are calorimetry (ISO 1716), TGA with DSC, SEM with EDAX and XRD. Each method has advantages and disadvantages and additional testing may be required in complex cases.

Step three: fire safety engineering

After the extent and location of ACP has been identified in step one, and the core components identified in step two, the next step is to forward all the information to a fire safety engineer. The fire safety engineer is able to assess all the information collected to assign a level of risk to individual installations, typically low, moderate or high. Generally speaking, low risk installations may be left in place with no intervention. Moderate risk installations may be able to be left in place with extra mitigations such as more sprinklers, relocation of possible ignition sources and so forth. High-risk installations are likely to need removal.

It is important to note that these recommendations do not take state legislation into account. Something that presents a low or moderate risk due to its location may still need removal if it comprises a cladding type banned by state legislation. For example, products with more than 30 percent PE are already banned in VIC and NSW with the requirement likely to be adopted nationally.

Step four: design of remedial work

Combustible cladding that requires removal should be replaced with a compliant alternative. If a close match can be found, this may be relatively straight forward. Some differences in colour might be unavoidable or changes in performance may be encountered. For example ‘oil-canning’ (rippling of the surface of the metal cladding) is a risk with thin-gauge (three millimetres or less) solid metallic sheeting – a problem not associated with ACP. There are a number of readily available non-combustible claddings, which may be compliant but which may not meet aesthetic requirements, and a good facade engineer would be able to advise owners of affected assets as to their options.

Other things to consider are that removal of the external cladding of a building is likely to affect its thermal and acoustic performance as well as its weatherproof nature. A competent facade engineer in conjunction with a good facade contractor will be able to adopt a program methodology, which can effectively manage these issues. If it is found necessary to replace the insulation, linings, or support structure, the replacement process is likely to be invasive and more costly.

Whatever the situation, significant work is required to ensure that any substitute cladding is installed in a competent and timely fashion, particularly if the building is fully occupied. The success and ease of the process will largely be down to the project team working on the design and replacement.

Detailed design drawings by a facade engineer suitable for tendering should be an output of this stage.

Final steps: tendering and implementation

The last steps are to contract out the works by inviting suitably qualified tenderers, with the facade engineer or a project manager generally acting as the interface between the facade contractor and owner. The implementation of works involves a project group comprising an owner’s representative, the facade engineer, the project manager (if required) and the contractor. For large or complex projects it is advisable to have a specialist project manager involved, one who understands the specific complexities of recladding operational buildings.

Resolution

Finally, with the combustible cladding replaced, the building owner can breathe a sigh of relief. The process can be daunting at the start, with much confusion and hype in the media. While straightforward, it is not a cheap process, and for some, it may seem beyond affordability. But can you afford not to go through it?

 

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