# Relieving Hydrostatic Pressure in Basement Walls



## dmeloche1 (Jan 2, 2012)

In the two years that I've owned my house, I've had two issues where heavy rain has resulted in water entering the the unfinished basement via the slatted jalousie windows. The windows are below ground-level and when the surrounding soil becomes saturated, the exterior window well (even with a cover) fills with water which seeps through the closed glass panes of the window and flows into the basement. The attached picture shows the arrangement of the basement.

I want to prevent the hydrostatic pressure from building to the point where it pushed its way into the window well and I've had a couple people recommend drilling relief holes into the base of the poured concrete walls near the floor of the basement. This would obviously let the water in the soil drain straight into the French drain but I've seen some articles online claim that these holes can work 'too well' and create a situation where the water pours through the wall in heavy rain, completely overwhelming the capabilities of the French drain and sump pump.

Does anyone have any experience with this particular problem? I don't plan on finishing the basement; I just want to be able to put things on the floor of the basement with confidence that they won't be floating around the next time a heavy storm rolls through.

Thanks!


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## nealtw (Jan 2, 2012)

Your showing the ground level in the window well at window level, this should be down about 6 to 8 inches and there would normally be a drain there connected to the perimiter drain which you don't have. If the water could travel thru the dirt fast enough it would be getting to your french drain now so adding holes at the bottom would not help much. I would lower the ground level at the window and core a hole at that level and pipe a drain down to your drain inside.


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## Jdmrenovations (Jan 3, 2012)

Just as Nealtw said, you need more space under the window, and a place for the water to go.  Digging out the window well much deeper and adding gravel can also give it that space to sit until it can work it's way down, but obviously a drain pipe down to the existing drain is the best solution.


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## dmeloche1 (Jan 4, 2012)

Thanks for the suggestions. My drawing is not to scale so the level of the window well is not very far below the window itself. This combined with the poor draining clay soil is a bad combination. So in addition to deepening the well you're both suggesting that I do something like this?







I wouldn't be able to dig down 8 feet to get below the foundation but could I instead Could I drill the hole through the basement wall like this, allowing it to drain internally to the French drain?






Thanks again for the help.


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## nealtw (Jan 4, 2012)

Your second picture is what I had in mind.


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## nealtw (Jan 4, 2012)

Maybe you have enough elevation to just pipe it away with out taking to the pump.


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## Jdmrenovations (Jan 5, 2012)

Was the drain put in after the foundation?  Is there an exterior (outside only, around the footing) perimeter drain system that you know of?

I ask because I see that white circle in the first drawing...is that meant to represent a perimeter drain?  If it is, and it is functioning as designed...not plugged, just tie to that.


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## dmeloche1 (Jan 6, 2012)

JFD, I should clarify that the last two pictures were just generic ones I found online. I was just using it to illustrate the drain line options from the window well. Unfortunately I don't actually have any exterior drainage system at all.


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## Jdmrenovations (Jan 6, 2012)

The option of bringing in the pipe as shown in the second drawing has only one tricky spot, mainly sealing the hole you punch through the wall.  Just be real careful with it, and seal it well.


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## Perry525 (Jan 9, 2012)

Your illustration indicates bad design.
Water should always be encouraged to flow away from a home.
I would suggest checking where the down pipes  are positioned and where the rain is directed from them.

If the water is coming off the roof, the down pipes should be terminated in sewage pipes to carry the water away from your home to a point downhill and below the level of the opening.
If your yard has a downward slope towards your home, you can either reverse the slope, or move the water round your home by digging an open ditch or French drain further out.
I would suggest in any event digging a hole near the wall to check on the ground water level.
If the ground water is high, you may need to re consider the existing internal drain and create a proper French drain outside.


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