Performance of non-incised CCA-treated hem-fir decking
P I Morris, J N R Ruddick
The question of what preservative penetration will provide an acceptable service life for treated wood in residential above-ground applications is topical in North American standards committees. Non-incised CCA-treated nominal 2 x 4 inch² hem-fir decking with penetrations close to the proposed CSA O80 2 decking standard of 80% over 5 mm, has remained without decay after 10 years exposure in south western British Columbia. Material with minimal preservative penetration showed early signs of decay. In contrast untreated unstained material had reached a rating of 1.1 on a 0 to 4 scale (0 = sound) with 12% of boards needing replacement. These results support consideration of a reduced penetration requirement in the standards for CCA treated decking.