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RH in Concrete for Wood Floor with Vapor Membrane
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03-26-2013, 06:13 AM #31
jim decker Concrete Moisture Enthusiast *
Status: Offline Posts:42 Threads:4 Joined:Nov 2011
Engineered wood ok to glue direct to concrete. Solid wood IF the boards are straight BUT generally one needs to use a screwdriver as a lever to get them tight together and then nail them. Dodgy

Also engineered wood can be blue taped to hold them in place until the glue sets while 3/4" solid..............Well just won't happen. Not to say it can't be done but success rate is diminished. Huh

Also most mfg don't advocate doing so and will wash their hands if it fails.Tongue

03-26-2013, 06:27 AM #32
CC Solutions Concrete Moisture Evangelist *******
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I don't do wood floors for a business, although I have put in a number of them.

I would shoot down a plywood substrate if I was working over a cement screed. That would eliminate the hollow sound a floating substrate has.

JD Grafton
Concrete Answers for Flooring Problems

03-30-2013, 11:33 AM #33
Ernesto Concrete Moisture Expert *****
Status: Offline Posts:606 Threads:33 Joined:Sep 2009
Franklin/Titebond has the only warranty that will replace everything, labor and materials if installed correctly. http://www.titebond.com/product.aspx?id=2535fe1a-43a7-493d-b451-a58d66d38736

There's a few manufacturers that have gluing down large lumber to concrete down pat. Carlisle is one of them. There's a lot that goes into it, especially the quality of the lumber and milling.[/align] I took the Carlisle certified master craftsman program exam. Lots to know about wood.

Also on the subfloor over concrete, shooting thousands of holes through any vapor retarder to fasten down plywood just is not necessary and in my humble opinion a reciepe for disaster. You can do a floating plywood subfloor and nail to that. Depending on the moisture tests and evaluation of the substrate and wether or not there is plastic under the slab and proper drainage I put down a trowel on or roll on vapor retarder under the wood, then 6 mil over top the vapor retarder. Then you will want 15lb felt on top the plywood. Some guys also put the felt under the plywood as well.

Stephen Perrera dba
Top Floor Installation Co.

04-29-2013, 03:58 PM #34
eaadams Concrete Moisture Expert *****
Status: Offline Posts:600 Threads:88 Joined:Jul 2010
(03-22-2013, 07:20 AM)jim decker Wrote:  Old post but just for the record NWFA and all hardwood manufacturer's require 75% RH or less utilizing insuti testing.

Jim - an update also. The MFMA (mapple floorin manufacturers of America) this month increased moisture tolerance for their wood floors from <=80% to <=85% RH.

I don't know if you as a NWFA Ceritified Hardwood Inspector fall under MFMA ... jurisdiction ... or not.

04-30-2013, 08:02 AM #35
jim decker Concrete Moisture Enthusiast *
Status: Offline Posts:42 Threads:4 Joined:Nov 2011
Information needed to advise
Is this engineered wood or solid?
How is it going to be installed glued direct or nail down over 3/4' Plywood.
What species of wood is it? Oak, Maple etc.
How wide and how thick?
What do the mfg's instructions advise?
I know of no wood that will allow 90% RH so what makes this one different?

Yes I saw that 85% requirement which NWFA will subscribe to. Anyway the nwfa is the authorative source for most manufacturers BUT as it is constantly drilled into us the manufacturers requirements if more stringent must be followed in all instances. For example we were getting ready to install a 5 1/2" wide x 3/4" thick solid brazilian chestnut an extremely dense hardwood and lo and behold perusing their instructions instead of 6" to 8" and within 1" to 3" of each end, NWFA and most mfgs, they required 4" to 6" and 1" to 3" first time I have seen a nailing schedule that tight.

05-01-2013, 07:20 AM #36
jim decker Concrete Moisture Enthusiast *
Status: Offline Posts:42 Threads:4 Joined:Nov 2011
The MFMA has revised the acceptable level of relative humidity in a concrete slab for non-glue down floor systems from <=80% to <=85%. This revision was made in response to feedback received from our contractor members during the past several years. The MFMA Technical Committee reviewed this information and felt confident raising the level to 85% based on contractor experience with successful installation of maple systems over concrete slabs with relative humidity level in excess of 80%.
MFMA continues to only recognize the testing of a concrete slab’s relative humidity levels using the most recent version of ASTM F2170. Please refer to the instructions of the manufacturer’s relative humidity test kit for details on how to administer the test correctly. MFMA now recommends that the relative humidity level for a concrete slag for a non-glue-down maples floor system is 85% or lower and for glue down systems the relative humidity remains at 75% or lower before installation. For concrete relative humidity conditions above MFMA”s recommendation consult your MFMA Sport Floor Contractor or your MFMA Manufacturer.
So this means a sports floor over screeds not glued to the floor 85% is allowable BUT for glue down floors 80% is the requirement. Remember this is for sports floors. Manufacturers of Maple floors for other than sports floors the requirement by all mfg’s of residential is 75% relative humidity.
One must be careful about what exactly is the situation!

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