Was my pre-2004 Ottawa deck built with CCA lumber?

If your Ottawa deck was built before 2004, Health Canada says it is likely to have been made from CCA-treated lumber, which stands for Chromated Copper Arsenate. There is no way to know for certain just by looking at it, but the pre-2004 date is the clearest indicator Health Canada gives.

CCA is no longer available for residential construction projects in Canada. The treatments used today are Alkaline Copper Quaternary (ACQ) or Copper Azole (CA-B).

What this means for your deck day to day

Health Canada has a few practical points worth knowing. Never burn CCA-treated wood, indoors or outdoors. When you saw or sand it, wear a dust mask, eye protection, gloves and long sleeves. For an older CCA deck that is still structurally sound, Health Canada suggests applying a sealant every year using an oil- or water-based stain. Paints and other film-forming finishes are not recommended on decking, and that applies here too.

The USDA Forest Products Laboratory notes that the most common reason preservative-treated decks get replaced is splitting and checking, not decay. Keeping water beading on the surface rather than soaking in is the best way to slow that process. A water-repellent preservative lasts about one to two years. Semitransparent stain lasts two to three years on new boards and three to six years on weathered ones. Both are US Forest Products Laboratory figures.

If you are thinking about replacing the boards or doing any structural work, the scope of that project will determine whether a permit is needed. The City of Ottawa requires a permit if the deck's walking surface is more than 600 mm (24 in.) above adjacent grade and the deck is attached to the house, or if it is an elevated deck providing principal access to the building. A deck under 600 mm that is not a main entrance and not on a designated heritage property may not need a permit, but the 2024 Ontario Building Code and the City's zoning by-laws still apply to the work.

If any repair or replacement work involves digging new footings, the next step before anyone picks up a shovel is to request a locate through Ontario One Call, which is free and required by law.