When it comes to flat roofs, fire safety is non-negotiable. And if you’ve ever worked with roof systems, you’ll likely have come across the term “Broof” (t4). It’s the gold standard in fire performance of roofs in the UK, but it’s also a standard that’s widely misunderstood.
What is BRoof (t4)?
Before the introduction of BS EN 13501-5:2016, the fire performance of roofs was assessed using the National Classification System, specifically BS 476-3:2004. This earlier standard focused on evaluating the durability and resistance of roofing systems to external fire exposure.
Broof(t4) is the highest classification under BS EN 13501-5:2016, the European standard for assessing the fire performance of roofs exposed to external fire. The classification focuses on two main factors:
- Spreading of flames
- Penetration by fire
To achieve Broof(t4), a roofing system is exposed to a rigorous series of fire tests involving burning brands, wind, and radiant heat – known collectively as Test 4. There are four test methods used to classify roof performance:
- Burning brands
- Burning brands with wind
- Burning brands with wind and supplementary radiant heat
- Burning brands with wind and direct radiant heat (t4)
Test 4 is considered the most severe. If a system passes, it earns the Broof(t4) rating – the best possible classification. The lowest classification is Froof(t4).
So, what does the fire test method actually measure?
The classification doesn’t just cover a single product. It applies to the entire roof build-up – from the structural deck through to the waterproofing and, for roof terraces, even the flooring finish. It’s important to note that there is a distinction between roof terraces and balconies under the Building Regulations. Balconies are officially classified as “specified attachments” to external walls (as defined in Regulation 2 and Approved Document B), which places them under the same fire-safety requirements as the external wall itself. This includes inset, projecting, access, and enclosed balconies – meaning that even frameless glass balustrades are now subject to these requirements, and many laminated glass types are effectively prohibited unless tested to the required standard (Gov.UK).
That means the test evaluates a complete system, not isolated materials. But here’s the nuance: if a component (like a pedestal) forms part of a tested and certified system, and that system achieves BRoof (t4), then that component is proven to perform safely within that system.
And yes, in many cases, the test allows for certain elements to vary slightly – for instance, the height of a pedestal. These are managed through what’s called an Extended Application Report (EXAP), which allows a degree of flexibility within the original test parameters.
What are the differences of European fire classifications against vs. Broof(t4)?
One of the most common misconceptions we see is confusion between Broof(t4) and Euroclass B. These aren’t interchangeable.
- Euroclass B is a classification under BS EN 13501-1:2018, which measures the reaction to fire of individual materials.
- BRoof (t4) is under BS EN 13501-5:2016 and assesses the fire exposure of roofs complete system when exposed to an external fire source.
So, while Euroclass ratings apply to individual materials (like membranes, boards or insulation), Broof(t4) applies to how those materials behave together in a real-world scenario.
Importantly, a system can include components rated as low as Euroclass F and still achieve Broof(t4) – provided it’s tested as part of a compliant build-up.
Are all systems tested? Not quite.
Are all roofing systems tested? Not quite.
Due to the sheer number of possible roof build-ups, it’s not practical to test every variation. That’s why certain roof coverings are deemed to meet Broof(t4) under specific conditions, without needing individual testing. These coverings are listed in the European Commission Decision of 6 September 2000, providing a recognised route to compliance for many common applications.
However, relying solely on deemed-to-satisfy solutions is not enough. The importance of full regulatory compliance cannot be overstated – especially when it comes to fire safety. Roofing professionals have a responsibility to ensure that systems meet the correct performance standards, and this includes staying up to date with guidance, obtaining appropriate training, and achieving certification where required. In fact, ongoing education and accreditation are increasingly seen as essential in helping reduce risk and raise standards across the roofing industry (source).
What are the limitations of roof coverings?
While Broof(t4) is the highest fire performance rating for external roof systems, it’s important to understand that not all systems meet this standard. Roofs classified as Froof(t4) offer little to no protection against external fire exposure. This distinction becomes particularly critical when considering the location of the roof in relation to a “relevant boundary.”
According to Approved Document B, the relevant boundary refers to the edge of a property where fire could spread to a neighbouring building, or to another compartment or plot within the same site. In practical terms, this includes not only site perimeters, but also divisions between different uses or tenancies within a development.
The distance between the roof and the relevant boundary determines what fire performance classification is required. For example, if a roof is within 6 metres of a relevant boundary, it generally must achieve Broof(t4) to comply with the Building Regulations. If it does not, such as in the case of an Froof system, it may pose a serious risk of fire spread and fail to meet regulatory requirements.
This is why it’s essential for specifiers and contractors to not only check a roof system’s classification, but also consider where and how it’s being installed. Misunderstanding the requirements related to proximity and fire classification can result in non-compliant and potentially dangerous installations (source).
| National Class | European Class | Minimum distance from any point on relevant boundary (England) | Minimum distance from any point on relevant boundary (Scotland) |
| AA, AB or AC | Broof(t4) | No minimum – can be used anywhere | Low Vulnerability (<6m) |
| BA, BB or BC | Croof(t4) | At least 6m from the boundary | Medium Vulnerability (6-24m) |
| CA, CB or CC | Droof(t4) | At least 6,12 or 20m from the boundary depending on the building type and use | Medium Vulnerability (6-24m) |
| AD, BD or CD | Eroof(t4) | At least 6,12 or 20m from the boundary depending on the building type and use | High Vulnerability (>24m) |
| DA, DB, DC or DD | Froof(t4) | At least 20m from the boundary depending on the building type and use | High Vulnerability (>24m) |
Our stance on the exposure to roof tests – and why we stand by it
When we say a component is part of a Broof(t4) compliant system, it means exactly that. We don’t claim the component alone holds the rating. We clearly state that it was part of a tested and certified system that meets the requirements.
We take compliance seriously. We test our products as part of full systems. We understand the legislation and when challenged, we can provide clear, accurate evidence.
Need help understanding compliance? We’ve got you covered.
Whether you’re specifying products or seeking clarification on fire ratings, our technical team is here to help. In this article, we’ve covered the evolution from BS 476-3:2004 to BS EN 13501-5:2016, the meaning and importance of Broof(t4), the difference between roof terraces and balconies, the role of deemed-to-satisfy systems, and why proximity to a relevant boundary affects fire performance requirements. Fire safety legislation can be complex, but you don’t have to navigate it alone. Get in touch with our team today – we’re always happy to guide you through the regulations and help ensure your project is compliant from the ground up. Contact us for more information.
