Wet Basements concrete basement wall and floor

Published on March 16th, 2017 | by Henri


Don’t paint a wet concrete floor

Q.    My home was built in 1937.  My cellar has both a concrete floor and concrete walls. I call it a wet cellar because after a very heavy rainfall water appears on the floor of the cellar. I leave nothing on the floor and the moisture eventually leaves on its own. The fact that the furnace is down there helps.

Here is my question. My painter wants to paint the cellar floor. I might be selling the house in a year or two and he thinks that painting the floor will help the cause. I am afraid that the paint will slow down the ability of the cement floor to dry after taking in water. Should I paint the floor? If so, what kind of paint should be used? Thank you.

A.    Painting the concrete floor is likely to turn into a disaster and make the sale of your house more difficult.
The leakage you are experiencing would simply cause the paint to peel. Moreover, concrete is a somewhat porous material, its porosity depending on how it was finished.

It is most likely that, in a house built in 1937, when technology was not as advanced as it is today, the concrete was poured directly on the soil without the proper stone bed and plastic vapor retarder. Capillary attraction, not broken by stones and plastic (or XPS foam, used today as a vapor retarder), is causing moisture to travel through the concrete and evaporate in the cellar, which would cause the paint to peel. My advice is to leave the slab alone.

The leakage after a heavy rainfall may be the result of deficiencies in grading and water disposal around your house. Most houses suffer from flat or negative grade around the foundation. In heavy or long-lasting rainfall, and when snow melts, water percolates down to the footings and finds a way inside.

Final grade should slope gently away from the foundation to drain water away from it, and be covered with a healthy stand of grass. Flowerbeds and shrubbery are best planted a few feet away from the foundation, as they encourage water retention.

Downspouts need to discharge on splashblocks that follow the grade’s gentle slope. Patios, walks, driveways, etc. must slope away from the foundation as well. If all those elements are properly done, the chance is great that leakage will be eliminated unless you are experiencing an underground spring or rising water table after a deluge.

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