Water in crawlspace, dug out too close to foundation, How to fix? Build a wall?

17512 Views 6 Replies 5 Participants Last post by walkman, May 18, 2009

twilightcall

Discussion Starter · May 17, 2009

Hi, I am having a problem with water getting into part of my crawlspace. It only happens after heavy rain that goes on for a few days. It never gets any higher than what is shown in the pics. The rest of the crawlspace is dry and doesn't get water. I think the problem is because the wall was dug out so close to the foundation. My plan was to install a sump pump but I am thinking that this would be a bandaid and not a repair for the problem. Plus I am worried that the dirt underneath the foundation may erode away over time as the water comes in and eventually cause a foundation problem. The house was vacant for 11 years so more than likely this has been happening for the past 11 years but I would like to fix it. I never noticed it until we started getting recent heavy rains. I went down during a heavy rain and it is definitely coming through the wall at the lower left section. My gutters are near new and draining properly so that is not the problem. There is no water leak in any of the plumbing either.

I thought about pouring a footer and building a cinder block wall about 1 foot away and motar the blocks. Then back fill it with dirt. I only wanted to make the wall as high as the main plumbing supply line? Is that high enough? Would this be the correct way to solve this?

What is the best way to keep the dirt under the foundation and keep as much of the water out as possible?

Is it still worth installing a high quality sump pump system just to be safe?

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oldrivers

· #2 · May 17, 2009 (Edited)

every new house that ive ever been in the last 20 some years has a sump pump so its not really a bandaid, its a legitimate part of the foundation , also you can make the dirt around your foundation slope away from it, also have rain gutters/ spouts direct the water away from the fouindation. i would defiantely install a sump pump though.

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walkman

· #3 · May 17, 2009

From the pictures, it looks like that section of the crawlspace was dug out after the house was built to relocate the water heater. Is that your impression?

And yes, it looks like the walls of the dig out would benefit from reinforcement to prevent the house from being undermined. In general, the bottom of the pit should be minimum 45 degree slope from the footers.

The walls should be properly reinforced with rebar/mortar for strength.

The walls should be appropriately waterproofed before backfilling with gravel. You can then determine if you still need a sump pump.

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twilightcall

Discussion Starter · #4 · May 17, 2009

Thanks for the info guys. It was dug out long before I owned the house. My guess would have been storage or something like that. The house is quite old.

So do you think about 1 foot away from the foundation build the wall. Put rebar in between the cinder blocks and pour concrete in the holes? Do you think gravel would be better than dirt?

Thanks.

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Daniel Holzman

· #5 · May 17, 2009

The water you are seeing is almost certainly groundwater seeping under the foundation walls. Building another wall will do nothing to reduce the groundwater level. The best way to deal with the problem would be to reduce the groundwater level, which would require you to dig a drain line around the house. Typically, this is done using 4 inch perforated plastic pipe installed in a gravel filled trench, typically about 18 inches wide, and about 12 inches lower than the lowest part of the crawlspace you want to drain.

This only works if you can run the drain line out to a lower elevation, which could be a low part of your lot, the street, or a catch basin if the town allows it. If this is impossible, you can install a sump pump, which will pump the groundwater out under pressure, again hopefully to a low point. Sumps work fine as long as the power does not fail, but they are not as positive as a properly designed and installed gravity drain system.

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yesitsconcrete

· #6 · May 18, 2009

holzman's probably right but { always 1 of those, right ? ? ?

} next time it rains, sprinkle some powder'd dye around the house & watch the crawl space for color change to be sure.

IF you can get uphill from where the wtr's infiltrating { typically 3' at least from the walls } backhoe a trench as he suggests 'cept line w/soil filter cloth & bed/cover the pipe w/clean 1 1/2" minus stone,,, 2" topsoil cover to hide the stone.

if you still get wtr in there, its hydrostatic

then we're head'd for a sump & pump,,, again, gravity drains're the best 'cause they'll still work when the power's off :thumbup:

holzman's pretty smart for an engineer, ain't he ? ? ? :laughing:

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walkman

· #7 · May 18, 2009

I think you're dealing with 2 issues. First the structural integrity of the house, and second the water infiltration.

Some people would punt on the first issue by claiming it's been that way for a long time. If you decide to address it, the closer you build the wall to the foundation the more you need an engineer/soil test to do it right. The general safe answer is to stay 1 foot away from the foundation for every 1 foot of drop. At 1 foot away from foundation for a 3 foot drop you are really getting into underpinning territory.

You should pour some kind of footer for the new wall and then rebar every 2 ft and fill cavities with mortar (or get an engineer to know you're doing it right).

The reason to use gravel backfill instead of dirt is that the water that is getting into your basement now will probably still be pressing against the new wall so you're going to have to have to handle it.

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Water in crawlspace, dug out too close to foundation, How to fix? Build a wall?

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