Acceptable percentage difference of moisture between the plywood and the wood?

Q: I am a wood flooring contractor. About seven months ago we installed a 4-inch red oak select floor with strip glue. We made sure before installing that the home was cool with air conditioning. However, they are experiencing some buckling. I had one of my guys remove a few pieces and the plywood is reading 15% moisture. I was wondering what is the acceptable percentage difference of moisture between the plywood and the wood?

A: The recommendation is no more than 4% difference. I wouldn’t worry if the plywood showed moisture content of more than 4% less than the oak but 15% is high. If this is a new house the entire structure may not yet have dried out. You know how through framing the place it can get rained on or filled with snow, etc. So it is a good idea to always check everything with a meter before you start. If it is an older home perhaps the plywood was stored out in the lumber yard not properly protected from the rain? A lot of people don’t realize how difficult our work really is.

Follow-up: Agreed, thank you for your response.

Moisture meter to test hardwood and subfloor

Q imported from our old site, Face Lift Floors: Have you ever seen a change with your moisture meter on hardwood flooring in just one week?

A: I wish I had one years ago, then I may have been able to answer yes.

However, I have not actually had such an experience. The main use I get out of it is to test wood when I take it to a job site, and before I start installing. I also use it to test the subfloor to make sure there is not a large discrepancy between the subfloor and the finished flooring to be installed.

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