Q: Hi. We are having a home built and there is a 4-ft.-high, 8 in. poured concrete wall for a crawl space foundation. When the forms were removed there was a serious crack in the wall (see pic). I’d like to better understand the cause of the cracking and any recommendations for repair before any further work progresses. Thank you , Mike
A: Diagonal cracks in a foundation wall often indicate a serious problem. They are typically caused by uneven settlement (or expansion) of the soil supporting the wall. If that’s the case, the settlement issue will need to be resolved before the crack is addressed. There are many possible causes for uneven settlement including low-strength soils, expansive soils, uncompacted fill, or drainage problems.
The soil may be stable now, or may continue to move. This could be due to preexisting building site problems or problems created during construction. For example, the excavation contractor may have overexcavated the foundation trench and filled it up to level with uncompacted fill. Or there may have been standing water in the trench when the footing was poured.
Depending on the type of problem, the soil might be stable now, or the uneven settling could continue.
I don’t see a footing at the bottom of the wall (see pic), which is a wide band of concrete which spreads the weight of the foundation wall over a larger area for better support.
In some cases, the footing is omitted if the soil is strong enough to support the building load without the wider base. Without a reinforced footing, however, it is difficult for a wall to bridge over a weak spot in the soil.
So the first step is to figure out the cause of the settling and address it. Sometimes weak spots under a foundation wall or slab can be reinforced with concrete, soil hardeners, or various forms of mechanical underpinning.
Once the settlement issue is addressed and foundation stabilized, the crack can repaired. The most common approaches are specially formulated patching cement or injection with a waterproof urethane or epoxy compound. Since this is fresh concrete, another option is to demo it and start over – although I’m sure that’s not the contractor’s first choice.
If you want authoritative information to help you negotiate with the contractor with, you may need to have an engineer take a look. He could propose effective ways to stabilize the foundation and repair the crack and also tell you whether a footing is needed – not an easy thing to retrofit. This type of work is often done by specialty contractors who focus on structural foundation repair.
You are 100% on target in addressing this now, before the framing goes up. If the foundation is cracking with no load applied, it will only get worse with the weight of a house on top. – Steve Bliss, BuildingAdvisor.com