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Basement Floor Cracks

You head down the steps into the basement and there it is. An ugly, menacing crack in the concrete floor. The more you stare at it, the larger it seems to grow. And when you’re really, really quiet, you think you hear it cracking even more.

What should you do? Keep staring? Keep listening? Or walk away and pretend you didn’t see it?

“Concrete is very complex,” says Bill Delamar, who owns a home inspection business and has inspected thousands of properties.

Delamar says many concrete cracks are just cosmetic problems. Sometimes the concrete creates its own expansion joint to accommodate slight movement of the ground underneath it. Sometimes the concrete wasn’t mixed with exactly the right proportion of water.

When he finds cracks during a home inspection he advises clients to bring in a structural engineer who specializes in concrete just to make sure there isn’t a larger problem.

What is Concrete?

Concrete is a paste that contains sand, stone and water. It can be manipulated into shapes just after it is mixed, before it dries, into something that is hard and durable. Because of its strength concrete isn’t just a choice for basement floors. It’s also used to build roads, bridges and high-rise buildings.

It is also very susceptible to cracking.

The Ready Mixed Concrete Association of Ontario says pre-construction preparation is the key to preventing cracks because all concrete will shrink as it cures. The proper configuration of construction joints can help prevent cracks as can proper preparation of the ground beneath the basement floor.

How to Repair It

Johnson Group Contracting generally fixes basement floor concrete cracks with one of two methods.

In the first, the crack is routed and smoothed, and then filled with polyurethane products that not only seal the crack, but allow for a little movement to occur.

A second and more expensive option that is often needed involves using an epoxy to fill the crack and bond the two pieces of concrete back together.

The different types of crack fillers and the tools to use them are for sale for DIYers interesting in repairing floor cracks themselves.

Why Repair It?

Basement floor cracks can become more than cosmetic nuisances.  They can be entry points into your home for moisture or even radon gas. Home sales are often not completed until crack repair is done.

If you find something on the floor that looks like the mark of Zorro, don’t panic. Most of the time a crack isn’t a serious problem and there are different types of fillers on the market to remedy the problem.

As one veteran builder tells it, there are only two kinds of concrete. The kind that is already cracked and the kind that is about to crack.

By Carla Turchetti

Interview with Bill Delamar, 2/17/12
Ready Mixed Concrete Association of Ontario
Johnson Group
Image provided by Emecole, Inc.

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