What do the experts have to say about wood-frame mid-rise construction?
- Graham Finch, Building Science Research Engineer
- Michael Green, Principal, Michael Green Architecture
- Mid-rise Wood Construction – a detailed look at a changing landscape (Part 1)
- Mid-rise Wood Construction – a detailed look at a changing landscape (Part 2)
- Seven-storey wood-frame earthquake test
- BC Housing is supporting wood-frame construction for seniors’ rental housing
Is mid-rise and tall wood building construction a new phenomenon:
Wood-frame and heavy timber construction (up to ten storeys) was the norm in the early 1900’s, and many of these buildings still exist and are in use in many Canadian cities.
- Check them out here: http://www.flickr.com/photos/bobkh/337920532/.
Over the past 10 years, there is a revival in the use of wood for both mid-rise (up to six-storeys) and tall buildings. In British Columbia alone, as of December 2013, there were over 250 five- and six-storey wood product based mid-rise buildings either in the design or construction phase.
Why have code change proposals?
This 2015 building code change is not about favoring wood over other building materials; it’s about acknowledging, via the highly thorough code process, that science-based innovation in wood products and building systems can and will lead to more choices for builders and occupants.
Are these buildings safe?
Regardless of the building material in question, nothing gets built unless it meets code. Mid-rise wood-frame buildings reflect a new standard of engineering in that structural, fire and seismic concerns have all been addressed by the expert committees of the Canadian Commission on Building and Fire Codes. As an example, when it comes to concerns from firefighters, there is increased sprinkler protection for concealed spaces and balconies, greater water supply for fire protection, restrictions on types of building claddings used and increased consideration for access by firefighters . In the end, when occupied, these buildings fully meet the same requirements of the Building Code as any other type of construction from the perspective of health, safety and accessibility.
What are some of the new safety provisions being proposed?
- Increased level of sprinkler / water protection:
- More concealed spaces sprinklered
- Balconies must be sprinklered
- Greater water supply for fire protection
- Non-combustible or limited combustible exterior wall cladding on 5th and 6th storey
- 25% of perimeter must face one street (within 15m of street) for firefighter access
Seismic and wind provisions:
- Similar to BC Building Code
- Guidance (Appendix) on impact of increased rain and wind loads for 5- and 6-storey
- Requirements for Apparent Sound Transmission Class (ASTC)
- Supported by science from FPInnovations, NRC and many others.
Doesn’t wood burn?
No building material is impervious to the effects of fire. The proposed code changes go above and beyond the minimum requirements outlined in the NBCC. Health, safety, accessibility, fire and structural protection of buildings remain the core objectives of the NBCC and wood industry at large.
What about construction site safety?
The Canadian Wood Council has developed construction site fire safety guides which outline best practices and safety precautions to take during the construction phase of a building.
How can building with wood be good for the environment?
Wood sequesters harmful carbon dioxide. Similarly to a garden, forests must be harvested so that the trees do not decompose and release their carbon dioxide back into the environment. With growing pressure for building designers to reduce the carbon footprint of the built environment, wood product based construction is a great choice as it is a renewable building material, originating from sustainably managed forests in Canada. A typical 2400 square foot wood-framed house has over 28 tonnes of carbon dioxide sequestered within the wood building materials products used in the construction of the building. That is the equivalent to the Carbon Dioxide (C02) emissions from a single passenger car driven for seven years, or 12,500 liters of gasoline burned, or the energy costs to operate the house for almost 4 years
Are mid-rise wood-frame buildings cost effective?
For the most part, yes. Mid-rise wood-frame buildings are often a less expensive construction option for builders. This is good news for main-street Canada where land is so expensive. The recommended changes to the National Building Code of Canada (NBCC) would give the opportunity to erect safe, code compliant buildings that would otherwise not be possible. The net benefit of reduced construction costs is increased affordability for home buyers. In terms of new economic opportunity, the ability to move forward “now” creates new construction jobs in cities and supports employment in forestry communities. This also offers increased export opportunities for current and innovative wood products, where adoption in Canada provides the example for other countries.