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RH in Concrete for Wood Floor with Vapor Membrane
03-17-2013, 07:40 PM (This post was last modified: 03-17-2013 07:46 PM by jim decker.)
Post: #21
RE: RH in Concrete for Wood Floor with Vapor Membrane
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.

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.
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03-17-2013, 08:25 PM
Post: #22
RE: RH in Concrete for Wood Floor with Vapor Membrane
Welcome Jim, nice to see you here.

I'm quite curious about setting RH% limits on the timber flooring itself for warranty specs, rather than just the adhesives or moisture barriers etc. Our peak industry body in AU is currently mulling over this issue now- what to stipulate as an acceptable lower level of RH for our timbers. Plus I'm assisting on spec sheets for some engineered boards.

So you are saying that you can warranty a solid hardwood against cupping and other moisture-related maladies below 75% ? What would you say about engineered boards and the slab RH- is it overly optimistic to say they are extremely stable on moisture uptake than solid or is that like asking "how long is a piece of string"? Big Grin

The problem with socialism is that you soon run out of other people's money.
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03-18-2013, 08:44 PM
Post: #23
RE: RH in Concrete for Wood Floor with Vapor Membrane
To further clarify wood is mfg between 6% and 9% moisture content. Mfg and NWFA recommend installing when MC is at midpoint some areas not possible due to extremes so must use moisture map of US additionally i.e. arid areas 4-8 or 5-9 El Paso. Florida 12% to 13%. All outlined in Bruce Hoadley's book Understanding Wood excellent reference for all wood questions. Charles Peterson better for installation info.
My website http://www.decker-consulting-inspections.vpweb.com has all of the NWFA manuals regarding hardwood floor installations. Check out http://www.buildingscience.com/documents...e-humidity regarding humidity questions.
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03-19-2013, 06:34 AM
Post: #24
RE: RH in Concrete for Wood Floor with Vapor Membrane
Yes, welcome Jim!
Good to see you post. Wink

JD Grafton
Concrete Answers for Flooring Problems
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03-22-2013, 07:20 AM
Post: #25
RE: RH in Concrete for Wood Floor with Vapor Membrane
Old post but just for the record NWFA and all hardwood manufacturer's require 75% RH or less utilizing insuti testing.
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03-22-2013, 01:36 PM
Post: #26
RE: RH in Concrete for Wood Floor with Vapor Membrane
You can do a floating subfloor
1 st layer, 3/8" exposure 1 plywood, is not fastened to concrete 1/8" gaping between panels.
2nd layer, 3/8" exposure 1 plywood, is laid perpendicular to first without no edges touching between them.
You then staple the 2nd layer to the 1st layer and proceed to nail to the 3/4" thickness required for nail down installation.
Thus you do not penetrate the vapor retarder.
This is approved by the NWFA and all mfg's in their instructions.
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03-22-2013, 02:19 PM
Post: #27
RE: RH in Concrete for Wood Floor with Vapor Membrane
One of the big manufacturers told me they were working on an even easier system a couple years ago. I don't know if it ever happened, but they were going to put down the vapor retarder and then pour a self leveler over it and glue directly to that.

JD Grafton
Concrete Answers for Flooring Problems
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03-25-2013, 05:20 PM
Post: #28
RE: RH in Concrete for Wood Floor with Vapor Membrane
Direct stick was *meant* to be the preferred, easier method here- moisture test, vapour barrier, then concrete adhesives then the timber. No penetrating anything. Low-foaming adhesives can fill out drummy spots in concrete up to (wild guess) 5mm if the slab is not too bad, but over that you need a levelling compound. So yes, you pour it over a vapour barrier and stick to that. But then if your levelling compound requires a feather finish, you have to prime the finish before trowelling out the glue, otherwise the glue won't stick.

Easy, right?! Tongue

Ah well, if this game was easy everybody would be doing it and then you'd be out of business JD..

The problem with socialism is that you soon run out of other people's money.
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03-25-2013, 05:44 PM
Post: #29
RE: RH in Concrete for Wood Floor with Vapor Membrane
Pat, please remind me, is being out of business a good thing or a bad thing??? Tongue

I could fish all day, shoot the bull in the pub all night! Exclamation

JD Grafton
Concrete Answers for Flooring Problems
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03-25-2013, 08:47 PM
Post: #30
RE: RH in Concrete for Wood Floor with Vapor Membrane
(03-25-2013 05:44 PM)CC Solutions Wrote:  Pat, please remind me, is being out of business a good thing or a bad thing??? Tongue

I could fish all day, shoot the bull in the pub all night! Exclamation

Sounds great. I may just join you...

The problem with socialism is that you soon run out of other people's money.
- Margaret Thatcher
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