Tricks for Treated Lumber
lumber holds so much moisture
that puddles form around the
heads of driven fasteners.
A Chemical Bath Starts the Process
The new breeds of PT lumber still start out as stacks of Southern yellow pine placed into large, sealed vats where air is evacuated and the preservative chemicals are introduced. The low pressure draws the chemicals into the sapwood. Because there is little chance for it to dry between its chemical bath and the time it hits the home-center shelves, PT lumber can have a moisture content percentage into the low-to-mid 20s. (Compare to kiln-dried hardwoods that average 6-8 percent.) Once left in your shop or a sunny spot, the drying--and the warping--begins.
The best approach to counter this: Let the wood acclimate outdoors in the shade for several weeks; then fasten it firmly in place with screws. One common mistake for beginning deck-builders is to leave a gap for drainage between the decking boards. This strategy isn't necessary for PT lumber; the shrinkage during drying will provide all the gap necessary.
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