Class "0" - What Does it Mean?

The Building Regulations Approved document B is very clear about the technical requirements for housing of multiple occupancy. The intention is for internal linings of communal areas to conform to Class "0".

Extract: from Building Regulations Approved Document B:

"The Requirements

Internal fire spread (linings)

B2.

(1) To inhibit the spread of fire within the building, the internal linings shall-

(a) adequately resist the spread of flame over their surfaces; and

(b) have, if ignited, a rate of heat release or a rate of fire growth, which is reasonable in the circumstances.

(2) in this paragraph "internal linings" mean the materials or products used in lining any partition, wall, ceiling or other internal structure."

Classification of Performance

The main classifications used are based on tests in BS476 Fire tests on building materials and structures, namely Part 6: Method of test for fire propagation for products and Part 7: Method of test to determine the classification of the surface spread of flame of products.

At the design stage it is sufficient for the selected products to have achieved a Class 0 rating over a non-combustible surface, i.e. skimmed plasterboard. However, many coatings that are Class 0 on a non-combustible substrate will not perform to Class 0 when applied over several layers of paint.

Warrington Fire Research Centre therefore provides a specially prepared board for testing for a redecoration application. This board, known as the Warrington Fire Research Centre "Blue" board is constructed using ten coats of different types of oil-based paints in order to simulate a previously decorated surface.

This means that products can now be tested over the "blue" board to achieve a Class 0 rating for use in multi-layer paint scenarios.

It is therefore important that Fire Test Reports be requested and checked to ensure that it is consistent with the intended use of the coating.