Can I fill Foundation CMU with dry cement?

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Can I fill Foundation CMU with dry cement?

Post by turtleshoe » Thu Nov 09, 2017 3:35 pm

I live in Raleigh, NC.

My house is build on CMU (Concrete Masonry Units) that are hollow from the footing to the floor joist. The CMU tend to fill with water and the water causes the dirt floor to get soggy. I am working on mitigating the issue on the outside of the foundation wall.

But I was curious if I could fill the inside of the hollow CMU (at least up to ground level) with something like powered cement or some other material that would naturally pack tight so that water will not fill in the bottom of the blocks.

I was thinking of even using sand to fill the CMUs from the footing to at least the ground level.

The water eventually dries out, but I want to keep the crawlspace dryer than it normally has been.

Screen Shot 2017-11-09 at 4.32.12 PM.png
Water in bottom of foundation . . .
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Re: Can I fill Foundation CMU with dry cement?

Post by Aaron » Thu Nov 09, 2017 4:59 pm

If those are filling with water, you have a bigger issue with drainage you need to attend to. I would ensure that the ground slopes away from the house and you may consider rain gutters (eavestroughs) with downspouts away from the house if you don't have them already.

Worse case scenario, you may need to trench around your house to the depth of your basement and adhere a water barrier around the perimeter of the house.

You could fill those holes with cement, but it would be pretty labor intensive and I'm not sure it'd be worth the trouble if you can successfully mitigate your water infiltration problem the right way.

However, if you do successfully mitigate the water problem externally, you could consider filling those cavities with styrofoam beads. That would give you some insulating value.

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Re: Can I fill Foundation CMU with dry cement?

Post by Shannon » Thu Nov 09, 2017 7:18 pm

yes I agree with Aaron you need to figure out what the issue is with the ground water and get it under control. You may need to also install a sump pump and sump pit it the issues is a high water table.
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Re: Can I fill Foundation CMU with dry cement?

Post by A. Spruce » Thu Nov 09, 2017 9:28 pm

I would agree, concrete wicks water, so regardless of leaving the blocks hollow or filling with concrete, you're still going to get moisture and/or water coming through the block. The perimeter drain on the foundation/basement wall is either nonexistent or has failed, so it is this perimeter drain that I would look at first. It may not be the cheapest method of remediation, but it is the best way, rather than trying to bandaid a problem that can't be bandaided.
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