Repairing a sinking outbuilding foundation

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Radio interview source: Dick Handy, retired professor of geotechnical engineering, Iowa State University

A few years ago, we noticed some shifting and sinking in our old barn. We had to jack up the barn to shore up the foundation and build concrete footings, and that's no small repair.

A barn or another outbuilding may sink for any number of reasons. Many older structures sit on stone slabs, with walls made of stone, which crumble over time. Some buildings have a log foundation, which eventually rots. If you have a newer building that is sinking, the problem may stem from a design error.

Dick Handy, a retired engineering professor, says the primary cause is simply the ground settling underneath a foundation.

"Hopefully it won't settle very far and usually an inch of settlement is considered acceptable," Handy says. "If the settlement is more than a few inches, it usually is uneven and we get cracking in the walls. It appears if the floor is coming up, but actually the structure is going down."

Other signs include uneven doors and windows, cracks in concrete, and separation of the building from the foundation. Handy says if you see this happening, it's time to call in an expert.