The importance of through wall fire testing

When you stop to examine any structure and its purpose, there is no getting away from the fact that fire resistance needs to be way up on the list of priorities when it comes to design. When you consider hotels, arenas, hostels, schools, universities, and homes, the need for these to be fire resistant is clear.

While there has long been an understanding of this need, and while fire-stopping products have long been available, there has been a clear shift when it comes to how these are now assessed. With BS EN 1364-1 standard to meet, and the Euro Class A1 rating, how these standards are deemed met has now changed.

It may seem obvious that structures should be built using non-combustible building material but, as we shall see, the obvious has not always been adhered to. For that reason, there has been a bigger focus on the use of of the likes of heat-resistant boards and fire-stopping boards. Beyond just a focus, there has been an increasing need to test.

Through wall fire testing has become a must when it comes to the design and construction of any building. We’re going to take a look at just what’s meant by through wall fire testing, what this involves, and why it matters.

Before through wall fire testing

Steel framing systems (SFS) are the go-to when it comes to any wall construction. This includes the likes of infill walling, continuous walling, load-bearing structures, and high bay walling. The appeal of SFS, for developers and designers alike, is that there are qualities such as being lightweight, versatility, and cost efficiency. These qualities have seen SFS be utilised for a wide range of development such as social housing, healthcare, residential, and more.

While there can be little denying that the qualities possessed by SFS are extremely desirable, the issue lies with the fact that these are almost worthless without some form of certification. Such certification is needed to prove that standards were met in terms of load bearing, thermal efficiency, acoustics, and, of course, fire resistance.

When it comes to SFS, the level of fire resistance is achieved by a combination of materials that are then combined within the SFS to make the wall. If you were to look at an external wall, this would typically be made up of dry lining, SFS, sheathing board, and insulation.

Historically, when assessing the fire resistance of a structure, data would be compiled from the manufacturers of each individual part. Each manufacturer would have confidence in the part that they had produced, but the combination of all of these parts was never tested as a whole.

The events of 14th June 2017 forced these practices to change.

The lessons from Grenfell

The events that took place at Grenfell can not be described as anything but horrific. The loss of life here was, without doubt, avoidable. While, of course, nothing can undo the tragedy that played out before us all on that day, there are still some big takeaways that can prevent a repeat. The biggest lessons here are that materials matter and that through wall fire testing is a must.

The issues faced at Grenfell are similar to those faced elsewhere: each part of a wall was awarded its own level of fire resistance. With each part reaching its own standard the assumption was that the wall, as a whole, was safe and that it was fire resistant. We now know that simply wasn’t the case.

The main structural component at Grenfell was concrete. This is well known as a non-combustible building material. Its levels of fire resistance are highly rated and it’s extremely unlikely to buckle under exposure to high temperatures.

The issue with Grenfell was the lack of fire-rated cladding. A 2016 refurbishment saw cladding added that primarily consisted of aluminium. This material, in terms of fire classification, just doesn’t meet any of the required standards. Not only does it lack in terms of fire resistance, but it is also highly conductive meaning that it would heat up extremely quickly.

The reality is that through wall fire testing would have revealed that Grenfell was a disaster waiting to happen. Fire-rated cladding and fire-rated external sheathing would have seen this scenario play out very differently.

What is through wall fire testing?

While assessing the importance of through wall fire testing, it’s perhaps important to take a look at what this actually means and the standards that it leads to. The first point to note is that, as it stands, there is no strict definition to state exactly what ‘through wall’ means.

The general consensus is that ‘through wall’ refers to the part of the wall responsible for the majority of thermal, acoustic, and fire properties. Usually, this will relate to the internal dry lining through to the outside face of the insulation or sheathing board.

The importance of through wall fire testing is simple. With such an array of external facade materials available, it becomes almost impossible to test every combination based on theory alone. Compiling the data from each individual element simply isn’t enough to provide a definitive assessment as to the true fire resistance.

With through wall fire testing, manufacturers are able to test, in practice, a combination of materials so that they can be assessed. The results mean that design teams are then able to make informed choices when it comes to the external facade. They have the data in front of them that proves that the required standards are met.

How is through wall fire testing carried out?

When it comes to assessing fire-stopping boards and passive fire protection, there are requirements that are set out in building regulations. These cover time performance such as how quickly smoke and flames can travel as well as insulation and load bearing.

In order to obtain the required data to show the levels of fire resistance, manufacturers need to submit samples to UKAS accredited labs. They do this by constructing complete wall build-ups that measure 3m x 3m. These consist of light gauge steel frames and then feature a range of fire-resistant boards and insulation.

Each of the wall build-ups are subjected to a high heat test. This sees temperatures reaching some 600 degrees centigrade in as little as 5 minutes. This heat exposure measures the performance of the entire wall by recreating the effects of fire breaking through a solid wall.

These through wall fire tests are carried out to BS EN 1364-1 standard. The only exception here is if the walls are non-load bearing where BS 476-22 comes into play instead. When these standards are awarded, it means that the walls achieve the 120-minute, 60-minute, and 30-minute ratings that are required by building regs.

Inside to out requirement

In the majority of cases, fire resistance is judged by an inside-to-out standard. This is because the aim is to stop any fire from spreading from its source and reaching adjacent properties.

However, there are also times when buildings are in close proximity to each other and in these cases, there also needs to be fire resistance from outside to in.

How Klasse Group reaches the standards

As a family-owned, British-based, company, we have always worked hard and strived to meet the required standards in the construction industry. When it comes to our external sheathing board, we are no different.

With though wall fire testing carried out by a UKAS accredited lab, we’re proud to say that what we produce exceeds the BS 1364-1 standard. Having just looked at how inside-to-out and outside-to-in fire resistance can hold equal importance, we’re pleased to say that in both instances, our product hits beyond the 90-minute standard.

Final thoughts

There is no escaping the fact that through wall fire testing has brought nothing but positives to the construction industry. The ability, and the need, to test a combination of materials means that the future of construction is one that focuses on safety. Of course, that should have always been the case, but the tragedy at Grenfell highlights that standards have not always been met.

What’s needed moving forward is for more manufacturers to commit to an approach that leads to certified wall constructions. As this happens, there will be a wider range of choices and solutions will also see an increase in flexibility. As things continue to develop fire resistance will remain the top priority, but there will be improvements in other criteria such as cost and even aesthetics.

Companies such as ours are early adopters. That means that, when it comes to navigating a way through understanding standards and specifications, we’re the ones that you need on your side. We bring extensive knowledge and experience that others are simply lacking and that means that we can provide you with nothing other than the best quality in a way that meets your design needs.

If you're looking for a reliable supplier for an external sheathing solution who cares about the safety of your project, contact us today with your project requirements:


T: 01432 842 030

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