Q&A for How to Unwarp Wood

Yep, the hubby's right. You may have to do it a bunch of times before the wood fully accepts its straightening, but it works and is done everyday.

I think only steaming/ironing is your only hope for that thinner stuff. Or, install it damp and with finish screws instead of nails and you'll be perfectly fine.

I doubt these exact methods would work, due to the amount of plastic in the composite. However, heat would be your best bet. Try wrapping black trash bags around the lumber and setting it in the sun.

A finish will keep the moisture from entering the cells in the grain, even when sanded to one degree or another. Heat and pressure methods shouldn't be affected by a coating though.