I am going to install composite decking on pressure treated 2x4 sleepers. The composite decking is attached via clips that slide in a groove of the composite decking. The clips only screw into the 2x4 sleepers.

Would it be better to buy the pt sleepers and let them warp in advance? I can then prune out the bad ones? If I put them in wet and screw the composite via the clips to the pt wood my fear is that the pt will warp but the composite won't be strong enough to resist the warping given it is really just floating on the pt sleepers.

The sleepers are sitting on a torch on membrane on flat and will not be fastened to the torch on or deck structure. The sleepers float on the deck and the composite more or less floats on the sleepers.

1 Answer 1


The pressure treated 2x4's need to dry out before using them especially if you'll be screwing those clips in for the composition decking. The boards will warp and shrink a bit as they dry out so buy a few more than you need. Save the receipt and return the ones that warp too much. You'll also want to seal the boards and you shouldn't do that before they are dried out.

  • In what way should PT lumber be sealed? Isn't that what the PT is for? Still gets my +1
    – FreeMan
    Feb 10, 2022 at 15:16
  • @FreeMan Howdy! wood is pressure treated with a chemical to protect it from rot and insects. This treatment is not, however, water proof. Once the chemical treatment has dried out, the wood should be coated with a sealer to protect it from moisture. This coating should be re-applied every few years depending on the type of weather. I have found out through experience, that the manufacturers over estimate the time between coats.
    – JACK
    Feb 10, 2022 at 16:21
  • Ah, that kind of sealer. That makes sense - I wasn't awake enough when I first read this. This is exactly the kind of sealing we do to our deck. We follow the mfgr's instructions of testing it by looking for water beading each year, and ignore their projected life span. ;)
    – FreeMan
    Feb 10, 2022 at 16:25

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.