Excessive moisture is a hardwood floor’s worst enemy. Moisture can
infiltrate your concrete slab from a variety of sources. The most common are sprinklers too close to
the home and overwatering, lack of appropriate rain gutters, other close sources of water such as
swimming pools, slow-leaking appliances, leaking pipes.
Whether you choose a laminate, engineered, or solid hardwood product, the key to a long-lasting
hardwood floor begins with a solid foundation. It is essential that the concrete subfloor be properly
prepared so moisture can be kept down to acceptable levels that will not affect your hardwood flooring.
This usually means applying a moisture barrier such as Bostiks MVP4 (Moisture Vapor Protection).
We asked our Bostiks MVP4 rep what she thought the number one cause for wood flooring installation
failure was, and her reply was no surprise: preparation. Bostiks has the best sealants and adhesives in
the industry, but if not applied properly even the best products can fail. Proper surface preparation
(roughing the surface) using the right equipment such as a shotblaster with a dust extractor is the
It is rare to find a problem with a final hardwood floor installation if the process was begun
properly with subfloor preparation.
Therefore, before a hardwood floor is installed, we highly recommend testing the concrete for moisture
content and applying a moisture barrier such as Bostiks MVP4. Most of the people we serve find that this
is a relatively small investment, well worth the longevity and beauty of their new hardwood floor.
Moisture testing methods:
- The visual inspection
Sometimes moisture in concrete is obvious to the naked eye. A visual inspection of the concrete
slab surface consists of identifying any of the following characteristics:
- concrete color contrast (dark and light areas)
- foreign material on the surface (heavy paint overspray, oils, previous sealant coatings)
- alkali buildup (white puffy, powdery surface material)
- Concrete Encounter CME4 by Tramex
This is a non-invasive method that we use regularly, in addition to doing a visual inspection. An
instrument with electrodes is pressed on the concrete and it instantly measures moisture levels in
the top 1/4 inch layer (range between 0% - 6%). This method identifies excessive moisture in
conjunction with the visual inspection, via a comparative method. For example, if dark and light
areas of concrete are visible we can measure the difference in those areas.
- Anhydrous Calcium Chloride Test
Today, many inspectors and installers still use this test to evaluate moisture content, either pre-
or post-installation. It is also non-invasive and takes about 3 days to administer. The calcium
chloride test tends to be accurate to approximately 1/2 inch depth in quantifying the moisture vapor
emissions from the concrete. It is more expensive and it can be biased or performed incorrectly,
which makes it subjective at best.
- Relative Humidity
This test involves drilling several small holes in the concrete and using an electronic sensor to
measure the moisture levels. It has been used successfully in Europe for many years, reducing wood
flooring failure rates, and it will most likely become standard in the US over the next few years.
It is also the most expensive to administer.
Next Step – Installation & Cleanup