January 23, 2012 at 11:34 AM

Before you can understand how to address garage floor cracks, it's important to have some foundational understanding of concrete itself.

Controlling Concrete Cracks

There is one distinguishing characteristic of concrete that remains troublesome to homeowners as well as contractors: concrete cracks. It cracks when and where it wants to. However, contractors can control concrete cracking to some degree by guiding where it will crack with a joint called a "control joint". When new concrete is poured and finished, control joints are either tooled in or cut in to "show" the concrete where to crack.

How Are Control Joints Placed?

There is a formula or rule of thumb that guides contractors where the joint is placed. That rule goes like this: a joint should be cut or tooled no further than two times the thickness of the concrete in feet. For example, if you have a 4" thick slab of concrete there should be a joint every eight feet. As with all rules, there are some exceptions and special conditions that cause the distance to vary but the fact still remains the concrete will crack where you place the joints.

Repairing Concrete Cracks

There is another cause for concrete to crack which is much more uncontrollable. When the ground under the concrete slab is settled, sunken, or washed out, concrete will settle and crack. When this occurs, it's best to have some mudjacking done to inject the voids under the settled concrete, thus filling voids and raising the slabs back to grade. You can then repair the cracks and restore your slab of concrete, which leads to our question about garage floor cracks.

Dealing with Garage Floor Concrete Cracks

How can you repair those pesky cracks in your garage floor concrete? As with many home repairs, there are several ways to achieve the same results. There are two main options. The first option is to caulk the cracks with a flexible concrete caulk available at most hardware stores or box stores. The correct material and preparation are the keys to a successful repair.

1. Clean excess dirt and debris from the crack you are repairing.
2. If the crack is deep use foam backer rod or silica sand to fill up the bulk of the crack leaving about 3/8" gap; this way you will use less caulk
3. Use a self-leveling caulk for the "touchless" finish.
4. Fill the crack with the caulk allowing it to flow to each side, making a bond with the concrete. Be careful not to over fill the crack.

The second method for repairing cracks is a bit more involved and utilizes an epoxy type crack fill. This method is used in commercial applications where more strength is necessary. The material cost is higher and a bit less user friendly then caulk. The result is still the same.