What should we do if there is evidence that there is high Moisture coming up our Concrete Slabs?


Have scratched the idea of replacing the old carpet we have left in the house. Bedrooms and Hall with a few closets, we found moisture under some plastic storage containers in the closets and remembered the wetness under an exercise bike mate sometime ago. There doesn't seem to be any mildew or mold signs or stains. Is the assumption that the carpet has let the humidity vapor through and not caused any major problems. Even the carpet under the plastic containers did not absorb enough moisture to feel wet or soggy, just the plastic and the top of the carpet where touching the plastic seemed to be wet. I pulled up part of the carpet to inspect and there is no stains or discoloration. The tiled and laminate part of the house seems fine but have no idea what lays underneath that can be called a problem. THe carpet is old and needs to be ousted, the tile and laminate is 15 years old with the tile looking like it did when installed and the laminate normal scratches here and there and a couple of water damaged boards under the freezer from either overflow or a lot of dropped ice under the unit.
Is it easy to say to just replace the old carpet with new as long as it can breath, as long as it can let the vapor escape?


ANSWER - Carpet might be allowing the moisture to evaporate through it, but as dirty as carpets get you could develop some microbial growth in the carpet.  Adding more carpet doesn't solve or prevent problems.

As your existing tile demonstrates it holds up well.   Ceramic Porcelain tile is more resistant to moisture. It can allow moisture to evaporate through the grout joints although you could develop efflorescence staining if there is excessive moisture.

Best bet is to replace with a porcelain tile. If the moisture in the concrete slab isn't excessive you can apply a liquid applied waterproof/crack isolation membrane over the properly prepared concrete and then adhere your tile to the membrane.

To verify the Relative Humidity of the concrete slab follow test method ASTM  F2170 or perform the Calcium Chloride test ASTM F1869.  Different manufacturer's have different requirements and limitations for moisture transmission.  If the moisture is extreme then you install a moisture mitigation product over the slab.  There are a number of different types provided by the various manufacturers of tile and stone installation products.

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