The NBCC requires that some buildings be of noncombustible construction.
Noncombustible construction is defined as: a "type of construction in which a degree of fire safety is attained by the use of noncombustible materials for structural members and other building assemblies."
Noncombustible construction is, however, something of a misnomer: it does not exclude the use of combustible materials but rather, it limits their use. Some combustible materials can be used since it is neither economical nor practical to construct a building entirely out of noncombustible materials.
Wood is probably the most prevalent combustible material used in noncombustible buildings.
It may be used as furring strips or fascia and canopies, cant strips, roof curbs, firestopping, roof sheathing and coverings, millwork, cabinets, counters, window sash, doors, flooring, studs and even as wall finishes.
Its use in certain types of buildings such as tall buildings is slightly more limited in areas such as exits, corridors and lobbies, but even there, fire-retardant treatments can be used to meet NBCC requirements.
In sprinklered noncombustible buildings not more than 2 storeys in height, entire roof assemblies and the roof supports can be heavy timber construction. Fire loss experience has shown, even in unsprinklered buildings, that heavy timber construction is superior to noncombustible roof assemblies not having any fire-resistance rating.
In other noncombustible buildings, heavy timber construction, including the floor assemblies, is permitted without the building being sprinklered.
Examples of permitted heavy timber construction uses in or, as an alternative to, noncombustible buildings are shown in Table 4.
|Table 4: Permitted uses of heavy timber construction in or as an alternative to noncombustible buildings|
|Group A, Div 1||1 Storey||Yes||Roof, floor and supports|
|Group A, Div 3||2 Storeys||No||Roof and its supports|
|Group A, Div 3||2 Storeys||Yes||Roof, floorand supports, arches supporting floors|
|Group A, Div 4||Not regulated||No||Roof and its supports|
|Group F, Div 1||3 Storeys||Yes||Roof, floor and supports|
|Group F, Div 1||1 Storey||Yes||Roof, floor and supports|
Brief description of other uses of wood permitted in noncombustible buildings can be found in Chapter 2 of Fire Safety Design in Buildings.