Above: Squash blocks installed to support load from above. Right: Load from above without squash blocks or blocking panels caused this web to buckle.
Natural High... on Stilts
A local builder uses piers to keep his 15 custom homes at Gifford Park high and dry as well as rock solid.
Worth the work: Piers support homes on expansive clay. Add insulated concrete form walls and stone hand-hewn on site, and Gifford Park presents worthy "parkitecture," says local builder Allan Staker.
Bentonite has the consistency of kitty litter and is about as much fun to build on. In Springdale, a town landlocked inside Southern Utah's handsome Zion National Park, bentonite-rich clay is hundreds of feet deep. But local builder Allan Staker, president of Springdale Development LLC, uses piers to keep his 15 custom homes at Gifford Park (www.giffordpark.com) high and dry as well as rock solid.
"It's much like building on stilts," says the former geologist, who entrusts lot-specific soil and load calculations to outside geo-technical and structural engineers. On a typical home, Striker buries as many as 40 piers 20 to 25 feet deep in the clay.
Pier quantity is as critical as depth and placement, because too many can do as much harm as too few. For example, insufficiently loaded piers can throw windows and doors out of plumb. Or worse. Staker reports seeing homes buckle under two-foot shifts, "so you better do this right or not at all."
Driveways, unsupported by piers, may shift and crack as the soil swells and shrinks. Done right, they and the adjacent houses won't budge.