Basement & Addition Digs in Salt Lake City, UT

Basement and addition digs are the excavation that comes first when a house grows: footings and foundation walls for an addition, a full basement under a new home, a dig-out beneath an older home with a crawl space, or a garage with a lower level. In Salt Lake City, where many neighborhoods were built before World War II on small lots, additions often mean working within a few feet of an existing foundation.

Frost depth sets the minimum

Salt Lake City and nearby cities such as West Jordan and Riverton publish a 30-inch frost depth. Footings for additions go at least that deep, and often deeper where the plans or soils report call for firmer bearing.

Working next to an old foundation

Digging beside an existing house is where most of the risk lies. Old stone or brick foundations can be shallow. We expose them carefully, avoid undermining them, and follow the engineer's sequence when underpinning is needed. HomeGuide puts excavation around an existing foundation at $5,000 to $15,000, or $100 to $250 per linear foot.

Clay and groundwater

Lake Bonneville sediments are often silty clay that holds water. Near the Jordan River and in flat areas such as South Salt Lake, the water table can be high. Deep digs may need pumps, drain rock under slabs and perimeter drains. We tell you when we expect water and price it.

Shoring and sloping

Basement excavations are deep enough to bury a person. Walls are sloped back, benched or protected with a trench box before anyone works below grade, and spoil is kept away from the edge.

What it costs

HomeBlue estimates a new-home basement dig-out in Salt Lake City at about $3,900 to $6,900 and a foundation without a basement at $2,400 to $4,100. National figures from HomeGuide run higher for full projects: $10,000 to $20,000 for an 8- to 9-foot basement and $20,000 to $45,000 or more to add a basement under an existing crawl-space house.

Spoil and access on small lots

A basement produces a lot of dirt. On small city lots there is rarely room to stockpile it all, so some is hauled immediately and backfill material is brought back later. We plan that cycle in the estimate so the price reflects real hauling.