Fixing Cracks in Concrete
A simple, permanent repair for cracked concrete walls
Concrete consists primarily of cement, sand, gravel and water. As the water in the slurry evaporates, the remaining ingredients cure into a hard, monolithic slab. Unfortunately, the curing process causes the concrete to shrink slightly, often resulting in hairline cracks. Larger stress cracks occur when a house settles or the ground beneath it shifts. These types of cracks typically don't threaten the structural integrity of the house, but they do create an entry point for groundwater, insects and radon gas. Here, we'll show you a simple, effective way to patch cracks in poured- concrete walls.
If you notice large, recurring cracks or bulging walls at your house, don't try to fix these conditions yourself. The cracks might indicate a more serious structural problem; call in a structural engineer for an in-depth evaluation.
Repairing the Crack
Several masonry patching products, such as hydraulic cement, do an adequate job of filling cracks in concrete walls. However, these concrete crack repair products can fail after a few years if your foundation or retaining wall continues to move slightly, leaving you with little choice but to chip them out and start all over again.
We repaired a foundation wall, which had an 8-ft.-long crack that leaked water into the basement during periods of heavy rainfall. To permanently patch the crack we used an epoxy-injection system from Polygem, called the Liquid Concrete Repair Kit (about $60). Each kit contains a two-part epoxy crack sealer, two 10-oz. tubes of Liquid Concrete Repair (LCR), a viscous epoxy that comes in a caulk-type cartridge, and seven plastic injection ports that deliver the LCR deep into the crack. There's enough material in each kit to repair a 1/16-in.-wide x 8-in.-deep x 8-ft.-long crack.
Before you start, check to make sure the crack is dry. If the crack is slightly damp, dry it with a blow-dryer, then wait 15 minutes. If it remains dry, proceed with the repair. However, if the dampness returns, water is still seeping into the crack and you'll have to wait for it to dry out on its own.
First, scrub the crack clean of any loose concrete, paint or old filler using a wire brush. Remove all dust and debris with a shop vacuum.