[Greenbuilding] Alternatives to Pressure Treated Wood

[Bruce Donelson]

Yes, you're right sleepers are used all the time. Plastic lumber
typically has very poor strength, so while it might be used for a
sleeper design (as long as it's "full contact"), I'm not sure I'd trust
it structurally, from what I've seen. I sort of like the concrete pier
ideas, except that everything has to be quite high to make space for
full-fledged structural lumber in that case. If you're using sleepers,
you should probably try to align them with the underlying framing
(unless they are across it), since if you've got 1/2" plywood sheathing,
it might not support the weight of your deck happily between rafters.

There is some borate & polymer treated wood that I've heard about but
haven't seen.

The Borate treated lumber will leach the borates out in the rain, so it
wouldn't be such a good bet for a roof deck. You would want something rated
for ground contact, because your roof might be very wet for some durations.

That said, the newer ACQ pressure treated wood is considerably less toxic
than the older CCA treated, which contained arsenic. But the copper content
of ACQ is more corrosive, so your fasteners and hangers need more corrosion
protection than fasteners into CCA wood did.

Bruce Donelson
A Better Builder