The National Building Code of Canada (NBC) requires that some buildings be of ‘noncombustible construction’ under its prescriptive requirements.
Noncombustible construction is, however, something of a misnomer, in that 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 and has numerous applications in buildings classified as noncombustible construction under the NBC. This is due to the fact that building regulations do not rely solely on the use of noncombustible materials to achieve an acceptable degree of fire safety. Many combustible materials are allowed in concealed spaces and in areas where, in a fire, they are not likely to seriously affect other fire safety features of the building.
For example, there are permissions for use of heavy timber construction for roofs and roof structural supports. It may also be used in partition walls and as wall finishes, as well as furring strips, fascia and canopies, cant strips, roof curbs, fire blocking, roof sheathing and coverings, millwork, cabinets, counters, window sashes, doors, and flooring.
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 NBC requirements. The NBC also allows the use of wood cladding for buildings designated to be of noncombustible construction.
In sprinklered noncombustible buildings not more than two-storeys in height, entire roof assemblies and the roof supports can be heavy timber construction. To be acceptable, the heavy timber components must comply with minimum dimension and installation requirements. Heavy timber construction is afforded this recognition because of its performance record under actual fire exposure and its acceptance as a fire-safe method of 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.
In sprinklered buildings permitted to be of combustible construction, no fire-resistance rating is required for the roof assembly or its supports when constructed from heavy timber. In these cases, a heavy timber roof assembly and its supports would not have to conform to the minimum member dimensions stipulated in the NBC.
Définitions NBC :
Combustible signifie qu'un matériau ne répond pas aux critères d'acceptation de la norme CAN/ULC-S114, "Test de détermination de l'incombustibilité des matériaux de construction".
Construction combustible désigne un type de construction qui ne répond pas aux exigences en matière de construction incombustible.
Construction en bois lourd signifie que ce type de construction combustible dans lequel un certain degré de sécurité incendie est atteint en limitant les dimensions des éléments structurels en bois ainsi que l'épaisseur et la composition des planchers et des toits en bois, et en évitant les espaces cachés sous les planchers et les toits.
Construction incombustible désigne le type de construction dans lequel un certain degré de sécurité incendie est atteint par l'utilisation de incombustible des matériaux pour les éléments structurels et autres assemblages de construction.
Incombustible signifie qu'un matériau répond aux critères d'acceptation de la norme CAN/ULC-S114, "Test de détermination de l'incombustibilité des matériaux de construction".
Pour plus d'informations, consultez les ressources suivantes :
Wood Design Manual, Canadian Wood Council
Code national du bâtiment du Canada
CAN/ULC-S114 Essai de détermination de l'incombustibilité des matériaux de construction
Stairs and storage lockers in noncombustible buildings
Wood roofing materials in noncombustible buildings
Wood partitions in noncombustible buildings
Wood furring in noncombustible buildings
Wood flooring and stages in noncombustible buildings
Fire stops in noncombustible buildings
Interior wood finishes in noncombustible buildings
