hydrostatic paradox

[Fred Smith]

I am purchasing a 50 year old home that has already had extensive interior waterproofing of the basement. There are still problems, however. For example, after a heavy rain water comes up through the concrete floor near the center of the basement, probably through some cracks.. Meanwhile, two sump pumps at opposite ends of the basement remain bone dry. There are french drains around all the inside perimeter walls and also several channels across the concrete floor, all to no avail. Has this house been built on top of a spring? What else could be the explanation?

[stevea]

Hi Fred,

It has been my experience that sometimes even with a full perimeter drainage system installed and tie to sump basins with pumps, that water will come up from the center of the floor or thru floor cracks.

I must say that this is rare. Some causes could be that ground water is following the water or sewer line that goes under the footing of the house and then under the concrete slab. Many times when the utility companies bring water or sewer lines into the basement, they will surround those pipes with sand or crushed stone, this makes for perfect drainage materials for the water to follow under the footing and then under the slab.

Very seldom would I say that the house was built over a spring. I would recommend having a drainage line go across the basement floor and then down directly to the sump. This should take care of the problem.

Perhaps the company who did the original drainage system would do this additional work or you could contact one of our NAWSRC member companies to give a look at your situation and give you an estimate.

Steve Andras
President NAWSRC