moisture test.
moisture test.
moisture test.
Test YOUR slab. Anecdotal evidence about other people's slabs is useless.
best method: Relative Humidity Probe Test - ASTM F2170
acceptable method: Calcium Chloride Test - ASTM F1869
Don't hire any installer who doesn't know what these are.
Then refer to manufacturer's acceptable levels.

Atelier is right on the money as far as moisture testing is concerned and it is best to slab test on or right after high humidity and rainy days to get the worst-case-scenario test returns.

The flooring system integrity will only be as good as it is in its worst day in the enviroment its installed in.

After you get test results and compare them to the manufacturers product tolerances, then you can decide on the right product for that application or other remedies to bring it to withing manufacturer tolerances.

The key here is prevention. Guessing isnt knowing, and any preventative measures used by guessing might be overkill OR might not be enough for the product. You just dont know without testing and in some cases an area will never be good enough for some products without rectifying the underlying construction causing the problem.

Yes, some adhesives and substrate treatments will add a water vapor barrier and stop or stem hydrostatic pressure in the substrate but they all have cap limits.

Owens Wood Flooring has a comptehensive information section of their site on Owens Plankfloor Gluedown Installation

Owens states the following:
"MAKE CERTAIN BUILDING INTERIOR AND SUBFLOOR ARE DRY

Interior walls should be dry enough to be painted and a room temperature as required by adhesive manufacturer with a relative humidity of 30-50% should be provided before any installation begins. To determine if a concrete slab is suitable for hardwood flooring, please follow the NWFA guidelines to perform a Calcium Chloride test. If excessive moisture is present, do not lay flooring. Check floor in several locations.

Concrete sub floors must be clean, flat and sound and of sufficient compression strength (3000lbs PSI) being sure that the surface is not slick. Sections not flat such as waviness, trowel marks, etc. are to be eliminated by grinding or the use of an acceptable leveling compound. Especially along the walls, the sub floor flatness must be checked and, if necessary, improved. Flat to 1/8" in an 8 radius. In addition to concrete sub floors, these products can be installed over dry, flat wood sub floors, such as plywood. If plywood is used as an overlay over an existing sub floor, the thickness of the overlay material much be such as to yield a total ¾" sub floor thickness.

New wood type sub floors should also be checked for moisture using a moisture meter. In general, wood or plywood sub floors should not exceed 12% moisture content or 4% moisture content difference between wood flooring and sub floor."

The NWFA is a resource you can only get information from if you are a paying member, so you might want to search around for the same information on calcium chloride tests from a independent source if you or your installer isnt a member.

It should be noted that there are different types of moisture testing.

1. Relative Humidity of the Installation Area.
2. Moisture in the substrate itself hydrostatic Pressure.
3. Moisture testing the wood looring itself before the install to ensure its equalized to the within-tolerance installation area humidity.

Here is some more information you may find useful:

moisture testing hardwood flooring
moisture testing for relative humidity in a room
hydrostatic pressure in concrete
ASTM F2170
ASTM F1869

your installer should be well educated in all of the above.

ask them plenty of questions and get a good comfort level in their abilities.

ask for and check out their references too.

Excellent info, thanks. What about seasonal changes or weather variations and slab testing? floorman, you mentioned to test ideally after rain. What if this is not possible? Is there generally lots of fluctuation in slab moisture? We are going to do the recommended test (Calcium Chloride) as specified by Owens, but there's no rain in the forecast! How valid then is this "snapshot in time" test in predicting future moisture issues in our slab?

use the Relative Humidity Probe Test - ASTM F2170
CaCl test is much more of a snapshot- the probe test has better predictive value

diysparky,

Dramatic changes in interior climate can affect a wood flooring system. If you can keep the relative humidity of the area under control you flooring system stands a much better chance of success.

Areas with high water tables, seasonally changing water tables with the wet part of the year being a high water table, and without proper slab construction techniques (like a dead-space or crawl-space under the slab are more apt to cause problems.

Slabs with proper moisture prevention under slab and those with dead-spaces and crawls spaces certainly fair much better.

IF there is any tell-tale signs like: musty smells, dampness, visible moisture, or mold growth at all then you may have issues.

As to seasonal and weather related fluctuations it all depends on your unique slabs and the construction techniques used in regard to moisture prevention.

If you never had any water or moisture problems there ot any of the above tell-tale signs, then it looks good but testing still should be done and this can be done anytime.

The snapshot should be valid especially if you ahve had no tell-tale signs of moisture previously.

Another thing to consider is proper product acclimation.

You want to acclimate you product to its enviroment by placing it in the isntallation area to equalize itself to its enviroment, and if it's plastic wrapped, cut open the plastic.

Test the slab.

Test the hardwood.

Test the humidity of the area.

Ensure all 3 are within recommenations for install.

Installation area relative humidity needs to be within 30% to 50%.

Area temperature should be within the adhesive manufacturers recommendations.

Hydrostatic moisture is not the same as moisture vapor emissions

Hydrostatic, is from being under the water table(basements) vapors are invisable and are always present in concrete.