A friend of mine is having 3/4" x 3 maple hardwood installed onto a plywood subfloor. The direction they would prefer the installation runs parallel to the joists. What is the minimum thickness the subfloor should be in order to install the wood parallel to the joists? Is there anything in the NWFA code that gives any guidance?

Thanks,
Tim

The parallel installation is addressed but the NWFA does not come flat out and state any minimum, if that answers your question.

Athough NOFMA does make recommendations for minimum subfloor thickness of plywood and direction to lay the flooring.
https://www.nofma.org/Portals/0/Publica ... rmance.pdf
https://www.nofma.org/Portals/0/Publica ... Floors.pdf

Thanks for the information. Has anyone ever had or heard of a bad experience laying a floor parallel to the joists?

A long time ago, they used to say you could install strip(2-1/4) any which way you pleased as long as you were going over 3/4 plywood. Problem is, there just aint that much 3/4 plywood going down anymore.

If I were istalling a 3in Maple paralell, I would want an extra layer of plywood. 3/8 would be plenty. Maple is a mover. When solid product moves across a single panel, wacky things can happen. The stuff can actually pitch and roll. It will jerk the plywood loose from the joists.

In a perfect environment, all of the caveats become irrelevant. Show me a perfect environment, though.

All recommendations are failsafes.