Testing times

The current version of Approved document B came into force in July 2001. Proposed amendments will harmonise Building Regulations with recently introduced European legislation. This will take the form of a European Supplement, which will identify the appropriate technical specifications and supporting European test standards. The Office of the Deputy Prime Minister expects to publish the European Supplement later this autumn. In practical terms, the effect is that materials will have to be tested in accordance with the European Standards, and classified appropriately. The new tests will measure fire reaction and resistance, and some materials may be reclassified as poorer performers than under the British Standards.

Fire resistance tests
A material's fire resistance is defined as its ability to withstand the effects of fire over a specified period of time without losing its fire-separating or loadbearing functions. It is used to test walls, columns, floors, doors and even ductwork.

In the case of fire-resistance tests on construction products, research shows that products tested by the European method record times that are, on average, 10-15% shorter than for those tested by the British Standards methods. For example, a product achieving 60 minutes under the British Standards test may only achieve 50-55 minutes under the European harmonised test.

The implication for the industry is that it will have to adapt its products, where necessary, to meet the 10-15% shortfall in test times.

For example, this may result in steel requiring more fire protection, or thicker sections of timber being added to achieve improved fire resistance.

Reaction to fire tests
The Euro-class reaction-to-fire data used for classification purposes will be derived from several tests, including the intermediate-scale Single Burning Item test with class limits derived from the larger-scale Euro-class reference test – the ISO 9705 Room Corner Test. This is capable of measuring "flashover" – the spontaneous ignition of combustible materials that causes rapid fire spread, a phenomenon that is not recorded by the UK's current small-scale reaction-to-fire tests.

Currently, the British Standard classifies materials as class 0, 1, 2, 3, or 4, with 0 denoting the best performer. With the European tests, the best performer will be classified A1, followed by A2, and then B through to F. The European Supplement to Part B of the Building Regulations is expected to allow the British system to run alongside the Euro-class system for a number of years.

Two additional hazards will be monitored during European tests to provide additional information relating to smoke (S1, S2 or S3) and flaming droplets or burning particles (D0, D1 or D2). At this stage such data will be available as additional classification rather than as part of the Euro-class criteria. At present, the Building Regulations do not refer to the potential for smoke hazard or burning particles.