What materials can you use on a roof terrace?
We often see the Fire Classification A2-s1,d0 associated with roof terraces and podiums, and this is not technically correct according to Approved Document B.
Why is it not correct?
A2-s1,d0 is the fire classification for a material’s reaction to fire and comes from the European Classification Standard EN13501-1. It measures a material’s combustibility when exposed to heat or fire, the level of smoke propagation when burnt and whether it produces flaming droplets. This classification relates to the external walls of buildings and specified attachments (such as balconies) as per Regulation 7.
Roof terraces, however, are not classed as specified attachments. Instead, they form the function of a roof and therefore, the classification A2-s1,d0, is not technically applicable.
If A2-s1,d0 isn’t the correct fire classification, why is it used?
The answer isn’t fully known. It could be due to a lack of knowledge in the industry as to what classification is required or that working to A2-s1,d0 offers a lower risk due to looking at the combustibility of products individually.
When designing a balcony or a terrace, working closely with your fire engineer and building control and product specialists will allow you to understand and develop safer buildings.
What is the correct classification standard for roof terraces?
When referring to a roof terrace, we need to use a different classification standard: EN13501-5. Part 5 of EN13501; the ‘Classification using data from external fire exposure to roof tests’. Part 5 classifies the roof build-up based on the level of fire penetration through the roof system rather than its level of combustibility.
The fire classification with an ‘un-restricted’ application for roof terraces is BRoof(t4). BRoof(t4) is an entire system test, so everything from the structural slab; through to the top surface; should be tested together. BRoof(t4) tests the whole system, so when an element of the roof build-up changes, there may be a need for a new certificate to cover that particular scenario. If an EXAP (extended application) report is published, it can cover certain variables within the roof build-up.
BRoof(t4) can be achieved for a roof build-up even when combustible elements are present, such as the waterproofing membrane, insulation, plastic pedestals etc. We also have the European Commission Decisions that can help us achieve BRoof(t4) without the need for testing.
