Are cracks in my basement floor a problem?

Certain small cracks in your basement's concrete floor may be the result of settling, or concrete's natural tendency to shrink when cured.(Photo courtesy of Angie's List member of Paul P. of Delaware, Ohio)

Certain small cracks in your basement's concrete floor may be the result of settling, or concrete's natural tendency to shrink when cured.(Photo courtesy of Angie's List member of Paul P. of Delaware, Ohio)

It’s fact that many houses develop cracks after they’re built. Most times, these cracks are referred to as nonstructural settlement cracks, but there can be a wide variety of reasons why a foundation cracks. Cracks can occur due to settlement of the building, concrete shrinkage and curing, stress and vibrations caused by trains and trucks traveling nearby, and bad construction methods.

In most cases, nonstructural cracks are divided into two categories:

1. Settlement cracks – Settlement happens when part of a house drops below the height where it was placed during the original construction. These cracks can be defined by the following:

  • If on the wall, the crack will be vertical, not horizontal
  • The crack’s width will be small, typically between 1/16-inch and 1/8-inch
  • The crack will not extend past the foundation into the structure

2. Shrinkage or curing – A poured concrete foundation may contain small cracks because concrete shrinks as it cures. The shrinkage tends to pull the concrete apart. Sharp corners at windows and doors are the areas where cracks often begin.

Are nonstructural cracks dangerous?

While a nonstructural crack is not threatening to the integrity of a foundation, it is still a potential problem because it can be letting water, moisture or soil gas into the home. Soil gases include air, water vapor and the pollutants that might be picked up from the soil beneath a building and carried by air infiltration into the building. The chief concerns among these pollutants are radon and methane gases.

How could air leakage come through our foundation and into the basement? A small insignificant looking crack in your basement wall could be letting radon into your home. These small cracks look harmless enough. After all there is no water leaking through it, it’s been there for years, hasn’t gotten any bigger. No big deal, right? Maybe it is. What if some colorless, odorless, tasteless gas was entering your home unobserved? The second leading cause of lung cancer (after cigarettes) is radon.

Why take a chance? Hire a professional licensed basement contractor to come in and permanently seal those cracks. With my company, common nonstructural crack repairs typically start at about $350. It’s a small price to pay for peace of mind.

About this Angie's List Expert: Doug Lynch is a basement expert from Westfield, N.J., where he lives with his wife Kelli. Doug teaches the Adult School class “Keeping Your Basement Dry” in six different towns to educate people how to have healthy basements. Doug is the owner of A-1 Basement Solutions in Scotch Plains, N.J., and the author of the popular Basement School blog.

As of January 31, 2013, this service provider was highly rated on Angie's List. Ratings are subject to change based on consumer feedback, so check Angie's List for the most up-to-date reviews. The views expressed by this author do not necessarily reflect those of Angie's List.

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Horizontal cracks caused by lateral soil pressure may eventually result in a bowed foundation wall, as seen in this before photo. (Photo courtesy of Angie's List member Lillian K. of Brevard, N.C.)

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I live in New England, every year when gets too cold I hear "small" explosion noises, I go down to the cellar and a new crack shows up on the floor... Should I worry enough to call my insurance and an expert ??? Could these cracks jeopardize the house structure??? I would appreciate your input. Thank you Wagner

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