Engineered Boulder Retaining Walls in Lehi, Utah

Most engineered boulder retaining wall projects in Lehi fall between $11,000 and $54,000, with large or multi-tier estate projects running higher. Where a project lands in that range depends on four things: wall length, exposed height (walls over 4 feet add stamped PE engineering, geogrid reinforcement, and permit fees), whether we are building on a raw slope or tearing out and hauling off an existing failed wall, and site access — yards with less than 5 feet of side access require compact equipment and smaller lifts, which adds labor time compared with lots that have 8 feet or more. Stone selection matters too: Traverse Quartzite, Utah Tan Fieldstone, and Dark Basalt vary in delivered cost and in how many tons it takes to build each foot of wall. Every quote includes the full 5-point drainage and base standard, so the number you see is for a wall built to last, not a stacked rockery.

Lehi City requires engineered retaining wall permits, third-party special inspection, and geotechnical compaction testing on Traverse Mountain walls over 4 feet. Under the International Building Code used across Utah, the 4-foot threshold is measured from the bottom of the footing to the top of the wall — not just the exposed face — so a wall that looks 3½ feet tall can still require a permit once the buried key-in course is counted. Walls that support a surcharge, such as a driveway, parking area, structure, or sloped backfill, typically require engineering regardless of height, and stacked tiers that are closer together than about twice the height of the lower wall are usually reviewed as a single taller wall. For any Lehi wall over 4 feet, we coordinate the Utah-licensed PE stamp, the geogrid design, and the permit submittal so the project is inspected and documented correctly.

In Lehi, we typically encounter highly fractured volcanic/quartzite rock mixed with collapsible wind-blown silt and expansive clay pockets on Traverse Mountain. Clay subgrades hold water and swell when saturated, so we never backfill native clay directly against the boulders. An 8oz non-woven geotextile separates the native soil from a 12"–18" chimney of washed 3/4" crushed angular drain rock, which relieves hydrostatic pressure before it can push the wall outward. Fine silts and sands migrate into open drain rock and wash out from behind the wall (piping), which clogs the drainage and undermines the boulders. The 8oz non-woven filter fabric is what keeps those fines in place while still letting water through. Where we hit fractured bedrock or rock shelves, we key the base course into the cut and step each lift back at an 8–12 degree batter so the wall leans into the hillside and locks under its own weight. Expansive, collapsible, or hazard-mapped ground is where taller walls most often need uniaxial geogrid tie-back layers and a geotechnical review, so the reinforced soil mass behind the wall acts together with the boulders rather than pushing against them. Most retaining walls do not fail because the rocks are too small — they fail because water and fine soil were never managed behind them. That is why our drainage chimney, filter fabric, and toe drain are standard on every Lehi project, not upgrades.

For Lehi projects we primarily use Traverse Quartzite, Utah Tan Fieldstone, and Dark Basalt. Traverse Quartzite is extremely hard and dense, resists freeze-thaw weathering, and breaks into angular faces that interlock tightly from lift to lift. Utah Tan Fieldstone offers a natural, rounded-to-sub-angular look; we orient each piece so its flattest faces bear on the course below. Dark Basalt is one of the heaviest stones available, ideal where a compact footprint still has to resist significant earth pressure. Regardless of stone type, the largest, heaviest boulders go in the keyed-in base course, each lift is set back at an 8–12 degree batter so the wall leans into the slope, and boulders are placed so they bear on at least two stones below rather than balancing on points. We can match stone to existing landscaping or HOA requirements in Utah County when a specific color or texture is required.

Yes. We build, repair, and replace retaining walls throughout Lehi, including Traverse Mountain, Silicon Slopes, SunCrest Ridge, Fox Hollow, and Canyon Hills. The most common problem we see in these neighborhoods is rapidly settling builder-grade boulder walls where unwashed dirt was backfilled directly against rock without filter fabric or drain aggregate. When an existing wall is failing, we remove it completely — including rotted timber, broken block, and contaminated backfill — then rebuild with a keyed-in road-base trench, a battered boulder face, non-woven geotextile separation, a washed crushed-rock drainage chimney with a perforated SDR-35 toe drain, and geogrid tie-backs on any wall over 4 feet or any tiered slope.