In one of our recent blogs we discussed the importance of fire safety for single ply roofing systems. As part of ensuring that your new roofing system meets the legal requirements and Building Standards, there are a number of factors to consider, including the classification of the roofing system. B Roof(t4) is the highest fire safety rating, but what does this mean?
Testing roof systems for fire safety and B Roof(t4) classification
One of the first things to understand about fire safety for roofing systems is that the entire roofing system is tested and rated as a full and complete build up. This means that the ratings of individual components are not as important as the rating for the roof in full. In practice, this means that all of the components, from the vapour control layer to the single ply membrane, will be rated collectively. As a result, no product can be swapped with another, unless the resultant new build up has also passed the correct testing.
What are fire performance classifications?
Fire performance classifications are important for rating roofing systems and ensuring that any new roofing system is compliant with the standards and regulations in place.
Before 2019, the National Classification System, BS 476-3:2004 was used to determine external fire performance for roofs. This is no longer applicable to roofing systems and instead, we now refer to the European Classification System BS EN 13501-5. This has five different ratings, including:
⦁ B Roof(t4)
⦁ C Roof(t4)
⦁ D Roof(t4)
⦁ E Roof(t4)
⦁ F Roof(t4)
What does B Roof(t4) mean?
On the above scale, B Roof(t4) is the highest rating, whilst F Roof(t4) is the lowest.
The new classification system, BS EN 13501-5, refers to four separate roof tests designed to establish the performance of a roof’s resistance to fire. These tests measure the penetration through the roof construction of external fire exposure, and measure the spread of flame over the roof’s surface. As such, the suffix ‘(t4)’ you see above indicates that Test 4 is to be used.
What is Test 4?
As the key test that determines a roof’s performance when exposed to fire, test 4 is very thorough. This can establish the spread of the fire, as well as the level of penetration. There will be a preliminary test which will involve examining one specific specimen, while three other specimens are assessed in the penetration test. At least one specimen containing samples of the joint details in each layer of the roof system will also be included in the penetration test.
So what do these roof classifications mean?
Using test 4 to measure the roofing systems performance when exposed to external fire has allowed the classification system to be developed. This allows roof systems to be ranked based on test 4 performance. The outcomes are as follows:
This is the highest rating of roof classification. During this test there will be no penetration of the roof system within 60 minutes. In addition, during the preliminary test, after withdrawal of the test flame, the selected specimens will burn for less than 5 minutes, and the flame spread will be less than 0.38 m across the area of burning.
During this test there will be no penetration of the roof system within 30 minutes. During the preliminary test, after withdrawal of the test flame, the specimens will burn for less than 5 minutes and the flame spread will be less than 0.38 m across the burning region.
During the test, this roof system will be penetrated within 30 minutes but this does not occur in the preliminary test. Instead, the specimens will burn for less than 5 minutes and have a flame spread of less than 0.38 m across the region of burning.
During the test, this roof system is penetrated within 30 minutes but is not penetrated in the preliminary test. However, the flame spread is not controlled.
This is the lowest rating of roof classification. No performance determined
For a B Roof (t4) roofing system that will meet all of your requirements, as well as fire safety standards, why not get in touch with the team at Enviroply Roofing today?