Wet Basements

Published on October 9th, 2013 | by Henri


Checking for water trapped in basement cinderblocks

Q.   I have a 1200-square-foot, one-level ranch home, 1955 vintage. When my wife and I bought the house twelve years ago, the basement was completely raw–poured concrete floor and cinderblock walls.

About seven years ago, I purchased some Sears moisture-proof basement paint and applied three coats to the basement walls and lapped it 6 inches onto the floor. Now, the basement is very comfortable, though we still run the dehumidifier three months of the year. I have carpeted most of the basement with low-pile industrial carpeting and a brown, wooly-looking pad. I also added a 12-foot by 12-foot section of ceramic tile in one corner under the washer/dryer. The ceiling is unfinished.

My concern is that I once read in your column that sealing concrete blocks is a bad idea because moisture can be trapped in the blocks and cause a mold problem. I would like to hire a professional to test for this and/or stick a little camera down in the block openings to have a peak and see if water is trapped in the blocks. Have you heard of any reputable companies that could do this type of evaluation? Do you have any other thoughts on this?

A.  Checking the cinderblock cavities is something you should be able to do yourself. It is likely that the mudsill on top of the blocks, and onto which the floor joists rest, is only 2 inches by 4 inches, as was common in the ’50s. The blocks are probably 8 inches wide (although, they should be 12 inches wide if the foundation is more than 5 feet below grade).

Using a stepladder, a mirror and a flashlight, check the cores of the blocks every few feet around the foundation. If you see any amount of water in any of them, it should be removed before it is likely to cause serious problems in the house.

This can only be done by drilling holes in the bottom of the vertical mortar joints of the base course using a masonry star drill and a hammer (or a cordless drill to avoid possible electrocution).

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