Small cracks in the concrete foundation or floor of your home probably don’t pose a structural problem but they are unsightly and can easily be a point of entry for water. Concrete repair is not all that difficult and can usually be done by anyone who has the basic DIY skills.
Concrete is made from Portland cement, sand and/or gravel and water. Once the component parts are mixed into a slurry it can be poured into forms or used as a slab. It hardens into hard, monolithic material, which unfortunately tends to shrink as it cures. This shrinkage is what causes hair line cracks to appear. As the house settles on its footings, larger stress cracks may appear, these cracks, although larger really do not have an effect on the overall strength of the structure, but they certainly are a potential entry point for seeping ground water, insect infestation and deadly radon gas.
The concrete repair of the hairline cracks can be done by the homeowner but it is highly recommended that the pro’s be called in if serious cracks or bulges appear, these may indicate a more serious issue that will require an in depth analysis by structural engineers.
Repairing the crack:
There are a number of commercial products available to affect concrete repair, some are better than others. Hydraulic cement is easy to use but usually fails again in a few years as the structure continues to move. When this solution fails, you have to chip out the old patch and redo it. A more permanent solution is to use two part epoxy which can be injected into the prepared crack.
To start:
Regardless of what method you chose to do your concrete repair, the crack must be dry. If it’s the least bit damp the fix will be less than expected. If there is a slight dampness, use a blow dryer and then a few minutes before you start. If it stays dry, proceed with the repair. If dampness returns all you can do is wait for the weather to turn and dry the crack naturally.
Then:
Loosen any concrete along the edges of the crack, scrape away any old paint or filler with a wire brush and then with a shop vac, clean away all remaining dust and dirt. To provide something to stabilize the filling material, drive 3” finishing nails into the crack, one each foot is sufficient.
Hydraulic cement can now be forced into the crack and the nails will support it while it dries. The best solution is two part epoxy. The application is best done in two steps, the first step is to run a bead down the length of the crack using the injector, the second pass is when the epoxy is spread with a putty knife or trowel.
