The performance of decking with relatively shallow preservative penetration is currently of interest to standards committees. A variety of non-incised nominal 2 x 4 inch decking was put into test by Forintek's Vancouver laboratory between 1981 and 1985. Two sets of non-incised CCA-treated hem-fir with preservative penetrations close to the 1997 CSA O80 decking standard have remained in very good condition after 21 and 24 years' exposure. These results confirm that the reduced penetration requirement introduced in 1997 provides effective protection from decay in above-ground applications. Decking double-vacuum treated with 0.5% PCP performed better than material dip-treated with 5% PCP when evaluated after 24 years in test. Following 20 years' exposure, decking treated with Arquad B-100 at 6.4 kg/m3 by uptake has performed as well as decking CCA-treated to the new CSA O80 decking standard. Untreated western white pine has performed better then hem-fir after 23 years' exposure.