Gap between wall and slab, seal it?

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Old 05-16-05, 05:37 PM
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Gap between wall and slab, seal it?

I am getting ready to finish my basement. I have seen people mention that they seal the gap between the basement slab and walls. Is this really a good idea? It seems the reason given is to prevent water from under the slab coming into the living area of the basement. However, if this gap is sealed and the water table is rising high enough that it wants to enter the basement then the hydrostatic pressure can become quite large and, it seems to me, heave the whole slab regardless of any sealing.

Plus, if in the future one of the concrete walls develops a small leak behind a finished walls (which will be built away from the concrete wall) I would rather have the water run down between the wall and slab rather than pooling somewhere in the living space.

Shawn
 
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Old 05-16-05, 07:32 PM
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between wall and slab, seal it?

You can try to seal it with a good flexible material or one of the non-shrink patching materials, but if you ever have any real amount of water build-up above the floor level you will probably have a leak. The performance of this type of seal depends on how well you prepare the joint and how well you fill the joint.

If you have enough water behind the finished wall, letting it drain out will not happen since you already have a saturated soil condition.

Make sure you have a dry basement in the first place. Correct the outside grading to insure water will drain away. Use downspout extenions.

If you are going to do a full-blown finished basement, I would consider putting in interior drain tile if you don't already have it. Interior tiles are more effective is preventing floor blow-outs from high water tables. I put in interior drains is about 4 weeks with my 12 year-old and his buddies, so it can be done when it is necessary. You will spend a lot of time and money on the interior finishing, so make sure you are starting with something acceptable.

Good luck!

Dick
 
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Old 05-16-05, 08:06 PM
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Thanks for the suggestions.

I believe I am doing everything necessary to keep water away from the basement before I finish it.

When we bought the house a couple of years ago it had (and still has) a sump pump/pit. I have since installed a gravity drain system using 4" PVC pipe connected it to the exterior drain tile and run it about 300 feet away from the house. At the time I also ran a 6" PVC pipe next to it and have connected all the back down spouts to it and will, in the next week or two, connect the front downspouts and the sump pump output to this pipe. I have also torn out a concrete patio that was sloping towards the house and I am going to regrade all around the house. I also have an interior drain tile.

Shawn
 
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