Basements

Published on October 29th, 2012 | by Henri

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Protecting basement from rainwater

Q.    For some time we had water coming into the basement during rainstorms. When the house was built, about 35 years ago, the builder put a pipe system around the inside periphery to catch water and direct it to a sump pump. Over the years, this system apparently filled with silt and this, together with a drop in the grading, allowed water, at times, to literally pour into the basement at the window wells.

About two and a half years ago, we had a new system of piping put in including drains in two of the wells so that the water flowed through a drain into a pipe and directly to the piping around the edge of the basement and into a sump pump which has battery backup. This system solved the problem of water coming into the basement very well, but we began to see damp spots in the cinder block walls and evidence of mold. Last spring, we had the walls painted with Drylok waterproofing paint. This seemed to contain the moisture, but now we are seeing staining on the walls in some areas and flaking with efflorescence.

We are concerned with the possible health ramifications of this condition. We are taking steps to remedy the grading problem and hope that by directing water away from the foundation, this will also help.

A.    Too bad you went to such an expense to have a new drainage system installed when re-grading would most likely have taken care of the water problem at considerably less cost. Drainage systems are an insurance policy against leakage if the grade settles over time and before it is repaired, and also in case of underground water sources. But proper grading is usually all that is needed to keep a basement dry.

For a drain system installed on the inside periphery of a basement’s foundation to stop working, it had to be connected to a similar drain system around the outside of the footings. Whether the silting occurred only in the outside drain system or in both the outside and inside systems, the results are the same. But water filling your basement window wells has to be because the drop in the grade you referred to is leading water into them — assuming that run-off from the roof is not involved. Re-grading outside when the weather permits should take care of that problem, as well as the problem of damp spots on the cinderblock foundation walls.

Painting the cinderblocks with waterproofing Drylok was, in my experience, a serious mistake. I have seen several cases where cinderblocks were waterproofed with various products without also making the necessary corrections to a negative grade. The result was that the cinderblocks filled with water and caused immeasurable damage inside the living quarters. The fact that you are seeing stains and efflorescence in some areas indicates that the block cavities are filled with water, and you have every reason to be concerned about any health effects.

At this point, the water in the blocks must be drained out and the only feasible way to do this is to use a star masonry drill (buy in a hardware store) and a hammer to punch holes manually in the vertical mortar joints at the base of the walls every couple of feet. Do not use an electric tool to do this, as the water will gush out as soon as the holes are punched through. Be prepared for a considerable amount of water draining out and resultant basement flooding unless you devise a system to contain the water in a channel along the walls and lead it to the sump pump.

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