Practicalities Often Overlooked in Combustible Cladding Remediation Design/Risk Assessment Stage

There have been a few external wall building fires reported again recently.

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This one in Brussels: https://www.dhirubhai.net/feed/update/urn:li:activity:7079831500015185920?updateEntityUrn=urn%3Ali%3Afs_feedUpdate%3A%28V2%2Curn%3Ali%3Aactivity%3A7079831500015185920%29

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And this one in the UAE:

https://www.dhirubhai.net/posts/grunde-jomaas-43149a86_facade-fires-sustainableconstruction-activity-7079747824757653504-0Gsm?utm_source=share&utm_medium=member_desktop

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It was the post from Grunde and comments on that post that was the spark for this article.

Grunde posed the question “What do you think is the right way forward with respect to this problem?”

Two comments caught my eye.

One was [my addition in square brackets]:

“Firestopping and compartmentalization acc [according] to ASTM codes. A clear fire strategy plan for new and existing bldg.”

With another commenter offering [my addition in square brackets]:

“It is easy to ban petrolium Based core ACP used in high rise buildings. But that is a solution for future. The main risk is buildings already built up with PP core ACP Fa?ades. The chance [change] is costy [costly] and No one wants it as a solution. Then what to do? I think we should think and discuss about active and passive fire stopping solutions. 2 or3 floor Fa?ade ACP changes rather than whole Fa?ade change or active fire prevention systems (sprinkler systems but the chemical used in systems is the most important) which is powerful against petrolium based fires. There May be more innovative solutions.”

There were a few things about these comments that caught my attention and that I thought were worth discussing.

“Firestopping and compartmentalization acc [according] to ASTM codes…”

While it’s a good idea to review and remediate the firestopping and compartmentation during a cladding remediation project, doing this alone is not likely to mean the combustible cladding can remain on the building.

I stand to be corrected but I don’t believe there is a respectable fire safety “code” in the world that permits highly combustible external facades on tall buildings on the proviso that firestopping and compartmentalisation are provided according to said “code”.

External fires bypass the internal firestopping and compartmentation measures. That’s one reason they are so high risk.

“It is easy to ban petrolium Based core ACP used in high rise buildings. But that is a solution for future.”

True. Australia has various bans in place now (due to having various states and Territories) and I’ve written on this before back in 2021:

https://www.dhirubhai.net/posts/aaronnichoslon_gg2021s022pdf-activity-6755628336573104128-KC0V?utm_source=share&utm_medium=member_desktop

?“We have had interesting discussions on this internally and my view is that this is an admission that it’s much easier to ban combustible cladding rather than address the cause of the problem, which is the building regulatory control system as a whole. This reduces the risks from combustible cladding for new works and new builds – yes it does. However, combustible cladding is not the only issue which the building regulatory control system as a whole faces – and by not fixing the system as a whole, the other issues (waterproofing etc) will remain.”

We can add compartmentation, firestopping of penetrations, cavity barriers etc etc to the list of fire safety issues that these bans are not resolving. Investment in education, training and regulatory oversight with teeth where required is necessary in my opinion.

?“…The main risk is buildings already built up with PP core ACP Fa?ades. The chance [change] is costy [costly] and No one wants it as a solution. Then what to do? I think we should think and discuss about active and passive fire stopping solutions. 2 or3 floor Fa?ade ACP changes rather than whole Fa?ade change or active fire prevention systems (sprinkler systems but the chemical used in systems is the most important) which is powerful against petrolium based fires. There May be more innovative solutions.”

There is no denying that in many instances, removing combustible cladding is very expensive.

This (quite rightly) leads people to consider if instead of full removal and replacement, whether implementing fire breaks or removing combustible cladding from two or three floors to break up the connected levels or runs of combustible cladding is a viable option.

It can be – but the details have to fall in your favour and until you have looked at the existing installation in a little more detail, you won’t really know. There is no point in coming up with a remediation option that cant physically be achieved on site.

Lets consider a building where the ACP is connected vertically and horizontally. It might look like this with each of the windows being hotel room:

So we might consider that an option to provide fire breaks might be to remove every other level of ACP or remove a level and keep two levels:

In order to understand whether these are a viable option, we need to know details about how the panels are fixed.

ACP cladding like this without visible fixings is typically mounted in one of two ways.

The first is cassette mounted.

?The ACP is bent or folded into cassettes which are then mechanically fixed to a hidden framework with the fixings themselves later hidden by backing rods and sealant which is where the distinctive (often black) sealant lines come from:

These are relatively easy to take apart and it might be that you get lucky and your sealant lines match the points where you want to remove ACP from to provide your fire breaks.

The second fixing method is tape fix.

These panels often have sharp edges with the core exposed and are flat stuck with adhesive tapes to the top-hat or frame.

Sealant is then added at the joints between panels.

There is no mechanical fixing of the panels in this system.

For tape fixed panels, lets say that the sealant lines land where we want to remove. What we have found is that the tape fixing can’t easily be cut or removed as the tapes adhere so well to the back of the panels that removal more often than not bends the adjacent panels (those we want to retain)?during removal efforts.

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"Cutting" of panels for either of the above fixing methods is a fire risk especially if Polyethylene (PE) cores are present and also leaves sharp edges and exposes the PE core even more.

As well as the above,?there are many other issues which may arise with the below being just a few of those:

• Can the replacement “fire safe” panel be made to fit the dimensions we have that are dictated by the existing installation?
• Can we achieve the same levels and planes with the new cladding? – i.e to avoid unwanted steps in the fa?ade which as well as unsightly, may give rise to weatherproofing issues.
• Often a change in top hats or battens is required for the new cladding. What are the implications structurally?
• What about the insulation behind the ACP is that combustible? If so, are we removing it from just the ACP fire break area and leaving the rest?
• Will the new cladding manufacturer warranty for the installation detail we are trying to achieve?
• It’s not likely that cavity barriers can be installed properly with these ACP fire breaks...so what do we do?

Lets just say that everything falls in our favour and we can perfectly achieve an ACP fire break to every other level or every third level like those shown earlier and the Risk Assessment back this option up for the building concerned.

In order to undertake these works, the building typically requires scaffolding to provide safe access.

With an ACP fire break rectification, the scaffolding will typically need to extend to the top of the building (or at least within 3 levels of the top depending on which ACP break option is justified).

This then begs the question that if we are already scaffolding to the top of the building to achieve the partial removal, what is the cost difference to just allow for the full removal? The scaffolding and setup costs (permits etc) will be the same.

For this reason, we often see the full removal option being taken when the costs are compared as the cost difference suddenly isn't that great but the benefit of full removal from a risk assessment or a psychological or even an insurance premium point of view becomes great.