Basement Floor Cracks

Basement floor cracks are common because all concrete spanned out horizontally cracks. It's just the nature of the beast. Cracking can be controlled with control joints but most basement floors are installed without them. Cracks are usually not of sign of any structural problems unless the open up wider than 1/4 inch or there is vertical displacement along the crack. If that does occur then you should contact a professional to investigate.

Most cracks in a basement floor can be left alone because they really don't pose any problem, especially if you're putting carpet down. There should be a vapor barrier between the floor and the subgrade so moisture won't be a problem.

If you're staining the floor then don't bother filling the cracks. It will just make them more unsightly and much more noticeable.

If you're putting down an overlay or tile, then you can treat the crack with an epoxy crack filler. This is not a guarantee that the crack will not tranfer through but it's worth the effort.

An epoxy crack filler does not necessarily have to fill the depth of the crack, but will provide a strong surface for heavy traffic. Narrow and hairline cracks need to be routed out first using a small angle grinder with an 1/8 inch masonry grinding blade. You only need to grind about a 1/4 inch deep.

Pour the epoxy crack filler along the crack and let it sit for a few minutes. You may need to add more as it seeps down through the crack. Then smooth it out at the surface with a trowel. If an overlay is to be applied, sprinkle sand onto the wet epoxy until refusal and vacuum excess the next day. This will give the new topping something to grab onto because it will not adhere to hardened epoxy. The epxoy needs about 24 hours to dry.

If you plan to paint the floor, then the hardened epoxy must be scuffed with sand paper prior to painting.

Just remember that you are treating basement floor cracks, not fixing them. There is no permanent fix for concrete cracks and there is always the possibility they will come back.