In Canada, use of treated wood is regulated by industry standards and by building codes. The Canadian Standards Association (CSA) produces the O80 series of standards for treated wood. The National Building Code of Canada (NBCC) is our model building code, adopted and/or modified for use by the various jurisdictions across the country. The NBCC contains requirements regarding the use of treated wood in buildings.
CSA O80 Series
The Canadian Standards Association is a private, not-for-profit organization certified by the Standards Council of Canada for the development of standards. The CSA Technical Committee on Wood Preservation oversees revisions to the O80 series of standards. This committee comprises representation from chemical manufacturers, wood treaters, government regulators, researchers, consultants and users of treated wood products. The CSA O80 series refers to a number of American Wood Protection Association standards for analytical standards and most preservative specifications.
Canadian standards for wood preservation are based on the American Wood Protection Association (AWPA) standards, modified for Canadian conditions. Only preservatives registered by the Canadian Pest Management Regulatory Agency (PMRA) are listed. The required preservative penetrations and loadings (retentions) vary according to the exposure conditions a product is likely to encounter. Click Here for a list of products and associated Use Classes extracted from the CSA O80 Series of standards and reproduced with the permission of the Canadian Standards Association. CSA O80-15 can be purchased through the CSA website.
The current version of the Standard, CSA O80 series-15, has been revised into the use class format which aligns it more with the American Wood Protection Association standards but uses the ISO 21887 Use Class system. Click here for a table of Use Classes and associated agents of deterioration, reproduced with the permission of the Canadian Standards Association. For more detail see CSA O80-15.
National Building Code of Canada
The 2015 edition of the National Building Code contains a number of references to preservative treatment:
- Pressure-treated wood conforming to CAN/CSA-O80.1 must be used for structural elements less than 150 mm from the finished ground level, or where they are not protected to exposure from precipitation, or moisture accumulation.
- In termite areas, pressure-treated wood conforming to CAN/CSA-O80.1 is required unless the clearance to the ground below is more than 450 mm and visible for inspection.
- Crib-work or retaining walls more than 1.2 m high or supporting building foundations must also be treated.
As with all other requirements of the National Building Code, the NBCC references to pressure-treated wood should be regarded as requirements to meet minimum standards of performance. The NBCC does not prescribe for all applications where pressure-treated wood may be used to prolong the life of the wood products in service.