In perusing the comments that I see regularly on the Internet, I am always amazed that people are still wondering why after they patch a crack it keeps returning. I see people’s frustrated comments about the crack returning time after time.
I see a variety of comments centering around almost everything except the real source of the problem. I see comments about moisture in the wood most commonly as well as framing and structural integrity comments. I am sure that some of those problems do play a small part, however the majority of crack movement causes in a house are caused from foundation movement.
So what causes the foundation to move? I had a friend in the road building business tell me once that all roads are dirt roads. It doesn’t matter when you paint the top of them with concrete or asphalt….the majority of the road is still made out of dirt. It works the same with foundations. If the soil under your foundation is not stable you will have movement in your foundation.
So why are the cracks moving so much? Sometimes cracks start moving when there has been no movement for 20 or 30 years. Other than the simpler problem of Sands and silts consolidating, there is the more complex problem of clay expansion and contraction. Clays expand as they get wet and contract when they get dry. If we have seasonal fluctuations in rainfall, or plumbing leaks, or any other changes in moisture, this variability affects the moisture content of the soil under a foundation, which then affects the movement of the foundation.
This explains why many cracks come and go with the various seasons. And it explains why here in Arizona with so much variation in seasonal rainfall why this issue is so prevalent.
If the soil simply moved back and forth the same amount every time it might not be so troubling. But that is not what happens. The soil tends to move over time on the downward trend with highs and lows along the way or it can move on an upward trend with highs and lows.
If you’re experiencing these issues you should have your home carefully analyzed in order to fully understand the problem so that a solution can be generated that will fix the specific problem being encountered.
Don’t accept a sales pitch from a commissioned sales person without engineering oversight.