By Alex Bardett, Managing Director at Ambar Kelly
With the Grenfell Tower tragedy bringing fire safety in higher risk buildings (HRB) sharply into focus, the role of riser shafts in reducing fires and improving safety has never been more important. However, they still face many misconceptions. Alex Bardett, Managing Director of Ambar Kelly, underlines the importance of educating the industry on the truth behind these misconceptions and the vital role that modular riser flooring can play in improving HRB fire safety.
When it comes to fire safety, the construction industry faces many challenges, not least a lack of understanding of the perils of installing combustible materials in any UK buildings. This is exacerbated by the perceived notion that non-combustible materials are more expensive.
As the Grenfell Tower inquiry highlights, the chosen material can have a significant impact on the spread of fire and smoke throughout any building – especially HRBs.
In fact, the tragic Grenfell Tower fire in 2017 involved a combustible material being lit and then, amongst other things, a fire rising in a void and forming a vertical shaft due to the lack of a horizontal fire break.
Furthermore, the King’s Cross station fire of 1987 involved a shaft ‘trench effect’, when a discarded match lit a combustible material and then developed into a ‘flash over’ due to the fire rising in the ‘trench’ of the wooden escalators.
While upcoming Building Regulation changes are set to sharply focus attention on fire testing and certification, more education is needed on the vital roles that non-combustible products play in improving fire safety in HRBs.
Upcoming changes to building regulations and fire safety
The Ministry of Housing, Communities, and Local Government (MHCLG) recently issued a new parliamentary statement that will see changes to fire safety and evacuation provisions, including Approved Document B. Fire safety information must be given to the relevant dutyholder when the project is complete or when the building is first occupied.
To further support enhanced fire safety from 2nd March 2025 onwards, the new updates will remove references to the national classification system for fire resistance, known as BS476. Parts 6 and 7 will require construction products to be classified in accordance with EN13501-1, with performance classes A1 and A2 for non-combustible products and B, C, D, and E for combustible products.
Non-combustible products are believed to be more expensive
Non-combustible steel plate materials, featuring pre-cut holes for M&E services that are covered by a lid, are often seen as being too expensive. While the initial cost will typically be more, that cost won’t increase as the project progresses.
However, the outlay for combustible GRP grating riser flooring options will increase over time, due to post-installation works. For example, GRP grating has to have holes cut into it to account for any services being fed through. Temporary fire doors will need to be fitted on every floor to meet codes of practice and prevent the spread of fire during construction, as by its very nature, grating allows smoke and flame to pass through. This increases the overall project cost.
Products are often labelled as having a fire rating – that doesn’t mean they’re not combustible
Specifiers will often see suppliers promoting products that have a BS476 Part 6 & 7 fire rating, which is actually a measure of the spread of flame.
This is typical for GRP grating used by UK contractors as a riser flooring solution. However, all GRP grating is combustible and will add fuel to any fire that occurs in a riser shaft. The Grenfell Tower inquiry found this surface spread of flame test (BS476 Part 6 &7) does not measure combustibility, hence why it’s being withdrawn on March 2025.
If the designed product for riser flooring in an HRB is specified as non-combustible at Gateway 2, contractors may believe the GRP grating has the required ‘fire rating’ and attempt to hand the project over to ‘Gateway 3’. However, despite it having a BS476 Part 6 or 7 declaration, it is combustible, meaning it will likely be rejected. Which leads us to…
Mistaken assumptions of responsibility (or lack of)
Often, a contractor will be under the impression that the product’s supposed fire rating is correct, handing over the project to the next person in the chain.
Indeed, there are many occasions when a main contractor will say ‘The sub-contractor has bought it and said it’s fire rated, so it’s not my problem.’ However, the situation isn’t always that straightforward.
Unfortunately, the main contractor will often hold all the risk and they won’t even realise they’re in this position. Additionally, if a non-combustible class A1 steel riser flooring product is specified in Gateway 2 and replaced by a combustible Class C GRP product, this needs to be recorded in the change control plan so the impact of these combustibility changes can be considered by the relevant teams.
Furthermore, it must be documented before the Building Safety Regulator (BSR) signs off the building for handover at Gateway 3.
Education is essential
Helping suppliers and main contractors understand the benefits of non-combustible materials will go a long way towards improving fire safety in the built environment.
The Golden Thread will ensure that anyone involved has up-to-date information readily available, ensuring a better understanding of the fire risks of using certain materials and the earlier identification of issues.
Industry leaders and the government also need to ensure quality standards are adhered to and regulations met. This will improve the quality of materials being used in construction for the benefit of the end user.
While it’s essential that contractors know their responsibilities if they change a specified non-combustible product for a cheaper combustible alternative, suppliers also play a huge role. Their products must be tested and certified to EN13501-1 to allow design teams and contractors to make an informed comparison between products.
With fire safety a vital aspect of any building’s construction, it’s imperative contractors are aware of the non-combustible opportunities, and associated benefits, available to them. They, along with the end user, will truly benefit as a result.
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