Cracks in concrete basement floor?

We’re renovating the basement in our 100-year-old brick rowhouse, and the contractor is concerned about cracks in the concrete floor. He says the proper fix would be to completely demolish the slab, excavate some dirt, compact the soil, install a moisture barrier, pour a minimum of 4” concrete with wire mesh and follow it with an epoxy coating. Anyone have experience with this? There aren’t any cracks in the walls. If it’s just cosmetic, we don’t care, but if the floor is gonna collapse or something, maybe we should do it.

Guest User | 6 years and 9 months ago

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Arkady | 6 years and 9 months ago

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I agree w/ Murph but would suggest steel studs, not pallets which can smell of mold & absorb water.

Smokychimp | 6 years and 9 months ago

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The contractor’s “fix” is not going to solve any problem. It sure would result in contracting profit, though.

If the perimeter walls and foundation are already in place, and moisture or differential settlement due to moisture/clay soil are causing the cracks, then what the contractor is proposing (it may hold for for a few years) transfers the water pressure and settlement to the joint between the old foundations and the new slab.

murph | 6 years and 9 months ago

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Probably means there will be infiltration by water at some time so leave nothing on the surface that you don’t want to toss later. Collect wood pallets and cut to size to keep any storage off the floor. Ditto utilities with cinder blocks.

Are you at a point in the topography that would indicate an under-the-surface flow of rainwater towards your foundation. Is the uphill roadway paved and sealed? Are there sidewalk cracks up to your foundation wall? Get some driveway sealer and fill in the cracks(better in warm weather when it will flow into the crack). This will lessen further infiltration but damp will rise so seal those cracks in the cellar.

Guest User | 6 years and 9 months ago

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Thank you! This is very comforting to know. I was worried that if we didn’t do the fix, our house would sink into the molten core of the earth. The contractor this morning was less doom-and-gloom, so we’re not going to do anything drastic. We’re planning to do polished concrete, and since the basement is basically a laundry and workout room, I don’t mind cracks.

resident2 | 6 years and 9 months ago

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It depends on what you want to use your “renovated” basement for.
if the cracking concrete floor that you have now does not have a moisture barrier, the cracks are probably caused by moisture rising through from the soil below; thus if you put rugs what ever on the the floors it may attract a damp, musty smell. If you are wanting to use your renovated basement to store your antique collections of photos etc. it will be a constant issue of controlling the humidity levels etc.
If all you are renovating for is as a cleaner storage space than you currently have for your seasonal storage of Christmas stuff / golf clubs etc, I would say leave it alone. Get a dehumidifier for major rain season.

GreenThinker | 6 years and 9 months ago

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it’s probably a 2 inch max concrete rat slab, totally normal to see cracks, (most concrete cracks) Sounds like this contractor just wants to take you for a ride.