Combustible sub-flooring and finished flooring, such as wood strip or parquet is allowed in any non-combustible building, including high rises. Finished wood flooring is not a major concern. During a fire, the air layer close to the floor remains relatively cool in comparison with the hot air rising to the ceiling.
Wood supports for combustible flooring are also permitted provided:
- they are at least 50mm but no more than 300mm high
- they are applied directly onto or are recessed into a noncombustible floor slab
- the concealed spaces are firestopped (as in Figure 10 below)
This allows the use of wood joists or wood trusses, the latter providing more flexibility for running building services within the space.
Stages are normally fairly large and considerably higher than 300 mm which creates a large concealed space. Because of this, wood stage flooring must be supported by noncombustible structural members.