Canadian Standards Association (CSA) use categories

The manufacture and application of wood preservatives are governed by CSA O80 standards. These consensus based standards dictate the wood species that may be treated, the allowable preservatives and the retention and penetration of preservative in the wood that must be achieved for the use category or application. 

The residential standards published in the CSA O80 standard have been developed to address the need for building code compliant treated wood products.  While many of the applications of treated wood in residential applications are not covered by building codes, there are instances where treated wood is used as a critical component of a structure (e.g. sill plates) and for this reason specified levels of treatment quality are required.

The CSA residential standards, unique to Canada, incorporate standards specific to residential applications into the use category system. These standards are referenced by the National Building Code of Canada and various provincial building codes.