Assessing Moisture in Concrete Subfloors
There are many avenues for moisture to enter a concrete slab, examples include:
- Ground moisture can enter through capillary action or as water vapour
- Groundwater might be present due to a high water table or poor drainage
- High air humidity
- High relative humidity in the environment
- Leaking plumbing that goes through the slab
Installing any type of floor over concrete that isn’t sufficiently dry can be disastrous and cause short and long-term issues. For instance, for wood floors, slabs with excessive moisture can cause:
- adhesive failure
- wood warping or cupping
- gaps
- creaking
- Floor coatings can suffer from blistering and delamination
- Mould and mildew are also common problems
You cannot look at the surface of a concrete slab and know if it is sufficiently dry to install a floor, it must be tested! Learn more about moisture in subfloors from the ATFA. This is an excerpt from Assessing Concrete Moisture by the ATFA:
“A great proportion of timber floors are installed over concrete these days and it’s a vital element of your subfloor preparation to assess the concrete moisture. Your subfloor preparation is the key to a successful install. Having the correct moisture meters and following the correct procedures are highly important. Likewise, don’t assume that an old concrete slab is a dry slab.”
Click here to view the Information Sheet #43, July 2014, published by the ATFA which will aid in clearly understanding these essential procedures.
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