Paver base & frost depth in Utah

Salt Lake County's frost depth — how far the ground actually freezes in a typical winter — runs around 30 inches. That number matters for anything built into the ground, because water in the soil expands when it freezes, and anything sitting above the frost line can get pushed and shifted as the ground freezes and thaws each winter.

A patio or driveway itself doesn't need to be built down to 30 inches — that depth requirement is specifically for structural footings (like a house foundation or a tall retaining wall). What it does mean is that the compacted base under a patio or driveway has to be built to handle freeze-thaw movement in the soil beneath and around it, which is why base depth and compaction quality matter so much more here than in a climate that doesn't freeze.

A patio built on a shallow, under-compacted base looks fine the first year. The freeze-thaw cycle is what exposes the shortcut — as the ground beneath and around the patio repeatedly freezes and thaws each winter, an inadequate base shifts, and pavers or concrete on top heave, settle unevenly, or crack. This is the single most common reason we get called out to fix hardscape another contractor installed a year or two earlier.

Taller retaining walls are a different case — they often do need engineered footings that account for frost depth directly, along with proper drainage behind the wall so water isn't adding to the freeze-thaw pressure in the first place. This is also where permitting requirements are more likely to apply.