HGS Engineering

Corner pops. They show up in almost every home inspection. Why are they so common and what causes them?

Corner pops are not caused by differential foundation movement, but rather thermal expansion. It occurs at the corner of the foundation and is extremely common on slab homes in North Texas with brick veneer. Occasionally, you will also see a vertical crack running straight up the brick wall form this corner of the foundation. When it gets hot outside and the materials expand, there must be a break point to relieve the pressure, and this triangular unreinforced corner is a weak point to break off. It is fairly important to patch these to maintain cover over the reinforcing steel, and does become a regular home maintenance item.

HOMEOWNER TIP! - Let’s talk about patching post tension cables. I put this in almost every report for homes built in the last 40 years. If you don’t know what these are, they are cables placed within the foundation. After the slab is poured they are tensioned to give it strength. After the tensioning process, the ends are cut off and patched. Because there is not much concrete cover over the steel water gets to them, they rust, and in turn the concrete loses its bond with the steel and spalls off (first picture). This becomes a regular home maintenance item and it is important to take care of. I have seen these cables rust far enough back into the slab to break the cables. Most of the time, people use a cement patch product to cover these. The problem with that is that it still does not have sufficient cover over the steel to prevent rusting, and that patch will once again lose its bond and spall off. I prefer recommending an epoxy. (Second picture) This is still cheap at your local hardware store, and while it may not blend in as well with the concrete, it will actually protect that steel from rusting and last much longer.

When looking into getting your foundation checked, you may have questions like why pay for an engineer?

Because nothing is free. A foundation repair contractor is not only unlikely to send out an engineer, but also be biased towards recommending repairs. Performing unnecessary foundation repairs can be mean bad news for otherwise well-performing homes.