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Vertical Cracks in Stem Walls

Cracking Goodyear AZ Stem Wall... what do they mean?

Almost every home we inspect (over a few hundred every month) has vertical cracks in the stem walls around it. For a description of a stem wall and what it is and its function, check out What is a Stem Wall?

Beware of any 'foundation inspector' who wants to pigeonhole every vertical crack as “proof” of foundation settlement.

So what are those cracks? Are they serious? What causes them?

First, let’s contrast that with horizontal cracks. These almost always point to a single cause…. Rusting of the horizontal rebar embedded in the concrete (see blog on this) unlike vertical cracks which have a variety of causes.

Cause #1: Rusting of vertical rebar, J bolts, or hold down straps. These cracks caused by similar steel embedments of horizontal cracks. Because these embedments are vertically oriented, the cracks from them reflect their positioning as well.

Cause #2: Shrinkage of the concrete. All concrete shrinks when it transitions from plastic (liquid) to a solid state as it sets up and hardens. As it shrinks, cracks form regularly… transverse to the long edge. To understand this think of a typical sidewalk. It has grooved joints every 4 or 5 feet. These joints are places for the concrete to crack as it shrinks. We don’t typically put crack control joints in stem walls, since the rebar tends to help reduce (but not eliminate) shrinkage cracks.

Not all soil movement is settlement.

Cause #3: Thermal cracking. As concrete expands when it heats up and contracts as it cools down, cracks form transverse to the long edge again, as it undergoes these stresses. Again very common and since it is outside of the home in a non-climate controlled area (unlike the interior slab of the home).

Cause #4: Movement from soil. As the stem wall settles or heaves, cracks can form vertically from this movement.

So as you can see, there is no smoking gun…. of a single “for sure” cause of vertical cracks. There are home inspectors in the Phoenix area that call out all vertical cracks as prima facie evidence of settlement. Not only is it false that all vertical cracks are caused by soil movement - as explained above - but it is also important to note that not all soil movement is settlement (as these same soil forces can heave upwards with just as much or more force as settlement).

Beware of any 'foundation inspector' who wants to pigeonhole every vertical crack as “proof” of foundation settlement. It's typical behavior of someone with a Dunning Krueger complex... someone who acts more confident to compensate for their lack of expertise.