Foundation Heave vs. Foundation Settlement
What is the difference?
Heave is the uplift of the foundation caused by wet, expanding soil beneath a slab floor. This uplift occurs when it is dry outside your foundation and wet underneath it.
It’s easy to misdiagnose foundation uplift problems because the edges of a slab appear to be pushed downward as the center of the slab is pushed up (as shown in the drawing above). The soil around your foundation can dry out easily because it’s exposed to the sun, the air and to plants that suck up moisture.
But these drying forces aren’t in play underneath a slab. Over time, moisture can easily accumulate under the slab from rain, roof runoff, leaks in nearby storm drains and other sources. So the expanding clay pushes up, causing central sections of the slab to move upward as well.
Settlement occurs when soils deform under the load weight of the foundation and structure built on top of it. Signs of a settling foundation can be very subtle at first -- many homeowners can go months, or even years, before noticing a crack in their foundation. The long-term damage from foundation settlement, however, is ongoing and will lead to more severe foundation problems.
Symptoms of a Foundation Problem
- Stair-step cracks in brick or concrete block foundation walls
- Leaning, tilting chimneys
- Cracks around doors and windows
- Jamming, sticking doors and windows
- Cracks in a concrete slab floor
- Cracks in drywall