Six-storey combustible construction now permitted

Volume 20, Number 1

The 2015 editions of the National Building Code (NBC) and the National Fire Code (NFC) now permit construction of six-storey buildings using traditional combustible materials (i.e., wood products). In the past, the Codes limited this type of construction to four storeys. The changes, 34 in the NBC and eight in the NFC, were developed in collaboration with industry, provincial authorities, fire services, research organizations, general interest groups and consultants in an effort to address their safety concerns.

The changes add limitations for building size and construction relative to the respective occupancy categories for residential (Group C) and business/personal services (Group D). They also incorporate additional protection measures to address the risk of injury due to fire and structural collapse in both the finished building and during construction.

Newly approved building types use passive and active protection measures based on concepts that are commonly found in other building types and that are addressed throughout the Codes. Passive protection measures include building height and floor area limitations and street access to a greater percentage of the building perimeter. Active protection is provided through automatic sprinkler systems installed in accordance with NFPA 13, Standard for the Installation of Sprinkler Systems. Even exterior balconies will now require sprinkler protection to reduce the risk of fire spread upward from one floor to the next through the surface of the exterior wall assembly. The physical dimensions of six-storey combustible buildings (including the roof) are also limited, allowing fire services access to as much of the building as possible.

Special attention has been given to the protection of these buildings during construction before the planned fire protection features, such as gypsum board, have been installed. Simple changes—such as signage for stair identification and labelling of street addresses—will help first responders shorten their response time. Enhanced fencing, boarding and barricades are also required to secure the construction site against unauthorized entry and arson, a major cause of fires in buildings under construction.

Occupancy combinations

The new code requirements for six-storey combustible buildings allow for a broad selection of mixed occupancies while restricting combinations that could introduce an unacceptable level of risk. Mercantile occupancies, as well as a subset of assembly occupancies, are permitted to accommodate stores, shops, restaurants, schools and community halls within the first two storeys. Parking garages are allowed underground and up to the third storey in order to account for increasingly common building design for mixed-use, residential buildings that also house businesses. High-risk industrial occupancies—such as chemical manufacturing, spray-painting operations, and bulk-storage of hazardous substances—are not permitted.

The response from the provinces and territories to these new building requirements has been positive. British Columbia, Alberta, Quebec and Ontario already have provisions in their latest provincial codes that allow construction of six-storey combustible buildings. British Columbia has allowed six-storey residential construction since 2009, with over 250 projects now built or near completion.

Contact

Sefton Hyde-Clark
Telephone: 613-991-4807
Email: Sefton.Hyde-Clarke@nrc-cnrc.gc.ca