Expansion Joint, Sealing Brick Can Cause Trouble

    By Dwight Barnett< Scripps Howard

    Q: I need a new concrete basement floor poured, but I don't want to have to move everything out.

    My contractor suggested doing it one half at a time by moving everything to one half, pouring the floor on that side, and then moving everything back to the other finished half before pouring that side.

    To do this, he suggested a floor with an expansion joint. Is this a good idea? He wants to treat the efflorescence on the 100-year- old brick basement walls with an acid wash, and then apply a waterproof coating/sealer. I thought inside brick needed a breathable coating. What do you suggest?

    A: A basement floor is subject to hydrostatic pressures, which is the force that pushes water up and against the floor. The lower the basement floor is compared to the outside grade, the higher the hydrostatic pressure will be.

    When you think of the basement as a boat sitting in water, you would not want an opening in the bottom of the boat because water would pour in. Even if you have never had a water problem before, having an expansion joint in the floor could be asking for problems. You can rent a storage trailer for your belongings on-site until the floor is finished.

    The efflorescence on the brick is an indication of moisture migration from the outside yard, through the brick to the indoor environment. When the mineral-laden moisture evaporates, it leaves behind a whitish deposit of minerals on the bricks and mortar joints.

    The wall can only dry to the inside of the home, not to the soils outside, so don't seal the bricks. You want to maintain the drying process and to do that you need to prepare the wall's surface to accept the moisture.

    Older masonry foundations have a sacrificial covering called parging. It will flake and fall off from time to time, which is normal. You can patch it but you cannot replace the bricks.

    DWIGHT BARNETT IS A CERTIFIED MASTER INSPECTOR FOR THE AMERICAN SOCIETY OF HOME INSPECTORS. WRITE TO HIM WITH HOME IMPROVEMENT QUESTIONS AT C. DWIGHT BARNETT, EVANSVILLE COURIER & PRESS, P.O. BOX 286, EVANSVILLE, IN 47702.

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