How to Handle Cracks in Your Concrete Foundation
This is the second of two articles on concrete problems.
Editor's Note: For concrete crack repair on walkways, see Jim Mallery's previously published article: DIY Concrete and Crack Repair for Patios, Walkways, and Driveways
Unlike cracks in concrete patios or drives, abnormalities in vertical concrete--the retaining wall or foundation---need to be taken seriously.
Of most concern would be bowing of the wall or cracking with uneven settling. If you have any evidence of this, you should consult a professional. You may have structural defects in the wall or serious soil problems that need to be addressed.
But even structurally sound walls on solid soil can develop cracks. You can expect minor settling over time; plus, concrete shrinks as it cures, causing cracking. As a rule, such cracks are usually vertical or diagonal, and usually are a little wider at the top, narrowing toward the bottom. If the crack is horizontal or is wider at the bottom, it could be caused by severe settling or structural problems and needs professional help.
If moisture is coming through the cracks, you should address that issue quickly. Water can cause further erosion of the concrete, and can lead to dangerous mold or mildew in your home.
First, you want to direct water away from your house. All soil should slope away from the foundation--absolutely no exceptions. Downspouts should lead to underground four-inch, unperforated drainpipes that will deposit rainwater a good distance downhill from your foundation.
If a moisture problem persists even though your soil is graded properly and your downspouts drained, you may have a groundwater problem and probably need to install a French drain.
A French drain is a simple construction, but very effective. A two- to three-foot trench is dug about three or four feet from the foundation on the highest two or three sides. Two to three inches of drain rock is put in the bottom of the trench. On top of that goes four-inch perforated plastic pipe (perforations down) and another layer of rock. The trench can be topped with soil. The pipe leads away from the house almost horizontally, surfacing naturally somewhere near the edge of your property.
The French drain should take care of your moisture problems, but you still have cracks to deal with. They can be filled by injection systems using either polyurethane or epoxy. There are many DIY injection kits on the market that a competent DIYer can use, or you can have a professional do it.
Remember, most foundation cracks are routine. You should be concerned about the cracks, but don't panic--usually, they can be repaired easily. And if not, you can call professionals who are ready to help.
Jim Mallery, a semi-retired journalist and onetime registered contractor, has extensive experience remodeling, repairing, and rebuilding homes.