The lowest allowed CRF for non-sprinkled buildings is 1.2 kW/m² and no requirement for some sprinkled buildings. For various locations and building types there is an increased CRF being 2.2 or greater or 4.5 or greater. The different levels are related to whether a sprinkler is installed and the mobility of the occupancy or closeness to the exit. The highest requirement is 4.5 for fire isolated exits.

As you can imagine there are many combinations of timber floors from parquet, strip, plywood, floating and exposed particleboard and plywood floors. Generic data is available from the timber industry for products that are not specific to the one manufacturer, for example tongue and groove (T&G) flooring or plywoods that are the one species. Floating floors and particleboard vary from manufacturer to manufacturer and the individual manufacturer should be consulted for this information.

The critical criteria for T&G flooring and parquet are the species and the thickness of the timber. There will be different CRF for different thicknesses within the one species.

Testing on various timber species and their performance is contained in Table 2 which is broken into two parts 12 mm and 19 mm thick for various species. For 12 mm flooring (i.e. parquet or strip) there is a requirement that it be backed by particleboard, or placed onto a non-combustible substrate such as concrete.

A common mistake made by designers when specifying particleboard or plywood flooring under a carpet is to require the substrate floor to have a CRF. This is not necessary when the substrate is not the covering. In this circumstance, the Fire Hazard Properties will be required for the particleboard or plywood flooring substrate and the CRF will be required for the carpet. But when the carpet manufacturer tests carpet CRF data, the substrate being plywood or particleboard should be included, so check that this is so.

Refer to Warrington Fire Research reports SFR 41117.2 and RIR 21419.