RH in Concrete for Wood Floor with Vapor Membrane

[jim decker]

The only definitive testing for hardwood on concrete is insuti testing. ASTM 2170 requires 3 sleeves for the first 1,000 sq ft and then 1 for every 1,000sq ft. Probes are placed in the concrete and 72 hours later they are read for RH in the slab and temperature. For hardwood 75% or less is acceptable. I am an NWFA Certified Hardwood Inspector and following these guidelines will prevent most actions harmful to a wood floor. Mfg's guidelines may be more stringent and must be followed.
There are many different vapor barriers from plastic to asphalt paper. If you document your readings with a camera and they are within the above requirement there little chance you can be blamed for any subsequent failure. Failure to do so will. On my website you will find the full NWFA Installation requirements regarding installing all types of subfloors. Crucial you document, with a moisture meter the readings of the concrete or wood sub floor and document the readings of the hardwood as outlined in the mfg's instructions. Again document your readings and in 20 years I have never even had a client go to court because any lawyer will realize you followed procedures. Usually, installers don't, then they call me.
http://www.decker-consulting-inspections.vpweb.com
Complete installation instructions are on my website and in every box outlining installation, mfg warranty, and maintenance requirements.
Be sure to make the client aware of their responsibilities RH 30% to 50% temp 60 to 80 and never ever shut hvac completely. Not my rules theirs.

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There is no liability for water damage. Solid requires 3/4" exp 1 plywood over concrete and I have yet to see one that has been salvaged. NWFA states replace as the mc in the plywood will start mildew and mold @ approximately 22% and I have never seen water damage that low.