With this post, I am going to start with a new thematic series in which I will explain the tests that are currently applied for determining the performance of roofs exposed to external fire. The particularity of this thematic series is that there has not been a complete harmonization of this type of test and therefore it is possible to find up to 4 test methods to evaluate the fire behaviour of this construction system. It is therefore necessary to know the principles of application of the each one of the test methods as well as the test procedure and its classification criteria.
The first thing to know is that the test methods for determining the behaviour of roofs in the case of fire are included in a technical specification, not in a test standard. Therefore, its denomination will be CEN / TS 1187. For different reasons that I will not explain in this post, a complete harmonization was not possible and instead of having a single test method for the whole Europe, 4 methods of tests are available:
- Test 1: With burning brands
- Test 2: With burning brands and wind.
- Test 3: With burning brands, wind and supplementary radiant heat.
- Test 4: Two stages test method incorporating burning brands, wind and supplementary radiant test.
It should be clear that the test methods shown above do not imply any ranking order. Each test stands on its own without the possibility to substitute or exchange one for another. So and as you can imagine, each country will require a specific type of test and therefore, if you want to market the product in several countries and require different tests, you will have to test your product according to the test required by the national legislation of each country.
Throughout this thematic series each of the test methods will be explained as well as its specific classification system.
Test 1. With burning brands
This test method consists of submitting the material or product to the action of a basket filled with wood wool which it will be ignite before the test begins. It simulates the falling down burning particles from a fire in other building. For this test, 4 specimens with dimensions of (1800 x 800) mm are required, which will present different types of joints depending on the layers of the product.
Table 1. Types of joints for each of one of the test specimens depending on the number of layers of the product.
The types of joints are shown below:
- Type 1, Single central joint in the top layer parallel to the roof pitch. No joints are required in any other layer (including insulation)
- Type 2, Single joint in the top layer at 90º to the roof pitch 100 mm above the lower edge of the basket. No joints are required in any other weathering layer. A single central joint in the insulation parallel to the roof pitch shall be provided, where applicable. The joint shall extend from below the lower edge of the basket to 800 mm above the upper edge of the basket.
- Type 3, No joint is required in any of the weathering layers. A single central joint in the insulation parallel to the roof pitch shall be provided, where applicable.
- Type 4, A single central joint in the weathering layer parallel to the roof next to the insulation. No joints are required in any other layer (including insulation).
- Type 5, A single central joint in the weathering layer parallel to the roof next to the top layer. No joints are required in any other layer (including insulation).
A point of special relevance and it has a direct influence on the result is the pitch that the material or product will have when it is installed in the reality. For this reason, this test offers the possibility of testing with different types of slopes.
- Roofs with pitches up to 20°: Specimens will be tested with a pitch of 15°.
- Roofs with pitches more than 20°: Specimens will be tested with a pitch of 45 °.
- Specific pitch: In this case, the specimen shall be tested with the specified pitch, the results will be valid only for test conditions.
In addition and as it happens in other reaction to fire tests, there is a series of standard supporting decks in order to minimize the number of tests simulating substrates of a similar nature. The duration of the test shall be 60 minutes, unless the following conditions are met:
- There is no occurrence of fire (flames, glowing combustion, and smoke).
- The flames reach an edge of the specimen.
- Penetration through the roof.
- There is a risk to safety of personnel or impending damage to equipment.
During the test, the following parameters are evaluated:
- External fire spread
- Fire penetration and openings
- The extent and nature of the damage
Up to now, I have spoken only of test method 1 to evaluate the behaviour of the roofs in case of fire. But fire safety regulations do not require this information, they require a classification of the product or material. Therefore, roofs exposed to the external fire will be classified according to classification standard EN 13501-5. This standard will collect the criteria that must meet the roofs to be classified. Due to there are 4 different test methods, the classification will consider this singularity and therefore it should pay attention for avoiding misunderstandings. Now it is shown how to identify the classification according to the test method used.
- Xroof (t1): Test 1: Burning brands
- Xroof (t2): With burning brands and wind.
- Xroof (t3): With burning brands, wind and supplementary radiant heat..
- Xroof (t4): Two stages test method incorporating burning brands, wind and supplementary radiant test.
Where X is the letter that identifies the classification of the product or material.
Focusing on test method 1, we will have only two potential classifications, Broof (t1) and Froof (t1). The classification criteria for the previous classes are shown below.
Table 2. Classification criteria for test 1. Burning brands.
Finally, it is necessary to know that in order to meet with the requirement included in the Spanish regulation described in Building Technical Code (CTE DB SI section 2 on external propagation), materials occupying more than 10% of the exterior coating or finishing of the roofs areas must be Broof (t1).
- CEN / TS 1187. Test methods for external fire exposure to roofs.
- UNE-EN 13501-5. Fire classification of construction products and building elements – Part 5: Classification using data from external fire exposure to roofs tests
- Building Technical Code. Basic document safety in case of fire. June 2017.