Both the fire resistance and reaction departments investigate the fire behaviour of a construction element if it were to undergo an internal fire exposure. However, this does not indicate how a roof, a roof covering or a skylight may react if it endured an external fire exposure.

Such external fire exposures can be caused by an adjacent burning building and/or an external fire exposure. So here a specific scenario is taken into account.

Belgian interpretation of an external fire exposure

The Royal decree of 7 July 1994, lays down basic standards on the prevention of fire and explosions to be fulfilled by new buildings, it allows two approaches.

From annex 5 from this legislative document:

• The finish layer materials of the roof covering belong to Class A1. 
  OR
• The product and/or materials for roof covering show the characteristics of the Broof(t1) class, prescribed in the disposition 2001/671/EG, or are in conformity with the decision 2000/553/EG.

From annex 6 of this legislative document:

• The roof covering of the industrial building belongs to class Broof(t1).

This duality deals with the evolutions from the national approach to the European approach. The national class A1 should disappear entirely in the future and make place for the European Broof(t1).

European interpretation of the external fire exposure

De Europese standard ENV 1187: Test methods for external fire exposure to roofs" contains four different test methods, derived from existing national test methods. The methods are indicated by t1, t2, t3 en t4.

On European level the Broof(t1), Froof(t1), Broof(t2), Froof(t2), Broof(t3), Croof(t3), Droof(t3),Froof(t3) of Broof(t4), Croof(t4), Droof(t4), Eroof(t4), Froof(t4). classes are then used.

The type of index which is used depends on the country where a declaration is wished. This way France requires a t3 class, the Netherlands and Germany a Broof(t1) and England a t4 class while the Scandinavian countries rather opt for a Broof(t2).

Lots of Eastern European countries follow the German example and ask for a Broof(t1).

The t3 and t4 methods know several classes:

• Broof(t3), Croof(t3), Droof(t3), Froof(t3)
• Broof(t4), Croof(t4), Droof(t4), Eroof(t4), Froof(t4)

Almost all European countries refer in their legislation to the use of a Broof(tx).

Obtain an European class

The first step when choosing the class is to check in which countries the product will come onto the market. So a declaration according to one or more t1, t2, t3 and t4 methods.

Tests and classification are described in the following standards:

• The test standard: CEN/TS1187: "Test methods for external fire exposure to roofs"
• The classification standard: EN 13501-5: "Fire classification of construction products and building elements - Part 5: Classification using data from external fire exposure to roofs tests"

The test standard

The test standard describes 4 completely different test methods where the flame spread and flame penetration are considered as the basis criteria. Depending on the test method, several complementary measurements are being carried out.

Test 1: the method with burning brand
Test 2: the method with burning brand and wind
Test 3: the method with burning brand, wind and radiation
Test 4: the method in two steps, with burning brand, wind and radiation

There is no connection or hierarchy between the different test methods. Each test has no connection with the other ones.

The classification standard

Depending on the performed test, an interpretation of the test data can be done through the classification standard so that a classification can be attributed to the tested product. A test according to:

Test 1 leads to the classes Broof(t1), Froof(t1)
Test 2 leads to the classes Broof(t2), Froof(t2)
Test 3 leads to the classes Broof(t3), Croof(t3), Droof(t3), Froof(t3)
Test 4 leads to the classes Broof(t4), Croof(t4), Droof(t4), Eroof(t4), Froof(t4)

Developments

In CEN TC 127 following projects are being worked on:

• the preparation of an Exap standard to extend the field of application of test results and this to reduce the need to test all the product variations
• the development of one single test method in place of the current ones.