There’s a Crack in My Basement Wall! What Do I Do?

Cracks in basement foundation walls are an indication that something is wrong; they shouldn’t be ignored. Cracks mean that the walls have moved, and something is causing that movement.

The most common cause of movement is moisture, either moisture expansion directly (clay soils, especially, expand with moisture) or from frost expansion, when the water in the soil expands with freezing. The frost expansion is particularly powerful and it’s difficult to withstand the forces developed. The existence of cracks is essentially your notification that there is a moisture problem.


The only realistic solution approach is to keep water out of the soil. Other articles on this website address the issue of drainage, and other aspects of keeping the soil reasonably dry. Make certain that you act right away to eliminate the water problem and keep the foundation problem from getting worse.


The key to evaluating the extent of the problem is to measure the amount that the wall has moved. If you drop a plumb line next to the wall (or set a long level next to the wall in vertical alignment) you’ll almost certainly find the upper wall has some displacement in from the bottom, where the concrete floor stabilizes the bottom of the wall. The worst-case value of this displacement is what you are trying to measure. (This is for horizontal cracks as shown above, shear cracks, where one section of the wall is displaced relative to the next, are more serious and steps will need to be taken to stabilize the wall).

Corrective Action

This is just a “quick summary” to help you get started. It’s for the most common types of problems and for concrete block walls, which are also the most common. This is for single-family homes and duplexes, not for commercial property. For other situations, or if there’s anything suspicious, you should get an engineer’s opinion.

Displacement ¼” or less (OK).  This is effectively plumb, as close to perfect as a well-built wall, with soil pressure acting on it, can be. Any cracks that exist are likely from shrinkage as the mortar cured.


Displacement ¼” to ¾” (OK if it’s stable; sort of bad if it’s moving).  With walls that have moved within this range the questions becomes, “Is it actively moving, or stable?” If there’s evidence that is has moved, then it should be stabilized in place by adding interior beams (refer to the section directly below for more information about this process). If there’s no evidence of recent movement (the last 10 years or so) then stabilization is not required. If you’re not handy with a level or plumb bob, you can use a “dime gauge”; if the horizontal crack is less than the thickness of a dime the wall movement is most likely less than ¾”.



Displacement of up to 1” (Pretty Bad; must be stabilized in place).If a wall has moved more than ¾”, or is “actively moving” it should be reinforced in some way so that it is stabilized in its present position. Cracks will generally be about 1/8” in width. The reinforcement is typically to add interior vertical beams along the wall (at least in the areas that show movement and cracks) attaching them to the floor joists above, and into the concrete of the footing or floor below.


Displacement of more than 1” (Really Bad; Excavation Required).1” is the generally accepted cutoff for requiring excavation. If a wall has moved this much, excavation of the exterior soil is required, along with straightening, adding strength, and re-mortaring. Cracks in a wall like this will likely be 3/16” or more. If a significant number of concrete blocks are damaged, it may be necessary to re-build the entire wall.


Get an Expert Opinion

A Zerrecon engineer can look at your property, review the problem situation with you, and prepare a written report identifying the problem(s) specifically and giving an opinion as to the corrective steps that need to be taken, if any. We can give you a set price for the service (depending upon your location) so that you know exactly what the cost will be. Call for a quotation.

Other Helpful Information

If you want to gain a better understanding of foundation issues, we have a link here to an article, “Keep Your Basement Dry” written by Tom Feiza. This is a chapter in his book, “How to Operate Your Home” which we highly endorse and which you can order from his website,

For more detailed information, particularly for the Wisconsin area, we suggest you go to the website of WAFRP (Wisconsin Association of Foundation Repair Professionals at They post a document there titled “Best Management Standards for Foundation Repair” that they developed in cooperation with the Building Inspectors Association of Southeastern Wisconsin ( This is not a code, or required in any way for foundation repair, but it is an engineering document, such that if this standard is followed the repairs do not have to be custom-engineered. This is extremely valuable as it can avoid the cost of custom-engineering for each individual repair job.

Recommended Procedure.

  1. Develop a plan
    1. Inspect as necessary. Measure displacement. Identify moisture problems. Have a drain tile test conducted if drainage appears to be an issue.
    2. Specify exactly what needs to be done. Refer to the WAFRP standard (or other written standards) if possible, to reduce the amount of writing you have to do, especially if the repairs are fairly common. Repairs that are custom-engineered may require a lot of detail.
    3. Submit the specifications to at least two contractors to get prices. See the page on “Finding Contractors”.
    4. The contractor will apply for a building permit from your city. City building inspectors will monitor the work to make certain that it’s done to their satisfaction.

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