Finishing Your Basement? When And How Should You Repair Concrete Cracks?

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If your home has an unfinished basement and was constructed more than a few years ago, it's likely that the natural settling of the ground around your foundation has led to a few minor cracks or imperfections in your basement's concrete slab. While this settling process is natural and expected, unusually deep or wide cracks in your concrete slab can make your basement more susceptible to flooding and other potential structural issues if not repaired. If you're planning to finish your basement in the near future, repairing these cracks quickly so that you can install a new floor above them may be even more of a priority. Read on to learn more about the ways you can restore your basement slab to its original condition and create a strong, leak-proof base layer for your basement flooring.

When should you resurface your concrete basement floor?

Barring an unusual seismic shift, cracks or holes that have already formed in your basement floor are unlikely to shrink over time. Installing a floating hardwood or laminate floor over your concrete slab can help prevent subsequent surface damage (such as spilled water seeping into a crack in the concrete and later freezing and expanding), but it won't do anything to repair already-existing problems. By that same token, installing a carpet pad and carpet can help wick water away from the concrete beneath and will provide some cushion against damage from heavy items or appliances, but it won't fix existing damage. 

Installing solid-surface floors or carpet also won't prevent your concrete from continuing to expand and contract with the flux of your foundation -- so having your concrete floor patched or resurfaced before installing a new floor, even if your existing concrete slab only has a few small cracks, can help stave off problems down the road and give your new floors a solid, defect-free surface to which they can adhere. 

What are your repair options for a cracked basement floor? 

When it comes to concrete patching and resurfacing, it can seem difficult to find products that are meant for indoor rather than outdoor use. You may also be worried about the prospect of breathing in strong fumes while spending hours trapped in a basement without windows. Fortunately, advances in technology have helped create a number of innovative resurfacing products that are versatile and odorless enough to be safely used indoors as long as proper ventilation precautions are taken. 

If your basement has no exterior windows or doors, your ventilation should primarily consist of a set of box or industrial fans directed out the entry door and its upstairs counterpart. If you do have one or more windows, directing a fan at the window should be sufficient to prevent any ill effects and ensure your concrete dries as quickly and evenly as possible.

By choosing a low-VOC polymer-based concrete resurfacing product, you'll enjoy low to no fumes while getting a like-new surface. Although untreated concrete can dry to a rough texture that may require additional sanding or leveling after it dries, polymer-based concrete has viscous fillers that expand to create a smooth, rink-like surface after drying. 

After setting up your ventilation system, you'll want to use an electric sander to smooth out any rough edges in the cracks you plan to fill and wash away dust from the inside of these cracks before mixing your concrete product. Be sure the surface of the concrete is damp (but not soaked) before you pour and spread the concrete. Pouring polymer-based concrete into a dry or dusty crack can cause it to poorly bond with the crack's surface, reopening the crack beneath your eventual floor. You'll then mix the concrete in a plastic bucket and use a pointed trowel to fully fill the crack, leveling the surface of the crack at a slightly higher rise than the surrounding floor. After about an hour, the surface should be dry enough to give a final smoothing with a finishing trowel. Allow the floor to dry for a few days before installing carpet or hardwood over it to ensure no cracks reopen after fully drying.

If you feel you cannot do this on your own, contact a concrete resurfacing company in your area or visit websites like