Sloped Backyard Terracing & Excavation

Planning a Terraced Backyard

Terracing turns one steep slope into a series of level benches separated by retaining walls. Design starts with how you want to use the space — a flat lawn for kids, a patio off a walkout basement, raised garden beds, a path to a lower yard — and works backward to wall heights and locations.

The total grade change is divided among the tiers. Two shorter walls instead of one tall wall can keep each wall under the 4-foot permit threshold, but only if they're far enough apart. Each decision trades flat usable area against wall height, cost, and engineering.

Tier Spacing: The 2H Rule

When an upper wall sits too close to a lower one, its weight and the soil it holds press down on the lower wall's backfill. A common rule of thumb — written directly into codes in cities like Sandy and South Jordan — is that horizontal separation between tiers should be at least twice the height of the lower wall. Closer than that, the tiers are reviewed as one taller wall and typically require engineering.

Each tier is drained independently, with its own drain-rock chimney and toe drain, and each terrace surface is graded to shed water away from the wall below rather than dumping it behind it.

Cut-and-Fill Grading

Terracing moves a lot of soil. A cut lowers the ground on the uphill side of a wall; fill raises it on the downhill side. We aim to balance cut and fill on site so less material is hauled away or trucked in, which keeps cost down.

Fill isn't just dumped soil. Fill that supports a lawn, patio, or wall above is placed in thin lifts and compacted; topsoil, roots, and debris are kept out of structural fill; and heavy clay may be replaced in the reinforced zone behind engineered walls. Poorly compacted fill is one of the main reasons terraces and patios settle.

Cuts in collapsible silts, expansive clays, or mapped landslide areas get extra scrutiny, and many Wasatch bench cities require hillside grading review on steep lots.

How Utah Hillside Soils Shape a Terrace Design

The same slope can call for very different terraces depending on what's underneath it. We look at the soil before deciding how many tiers to build, how far apart they sit, and how much reinforcement each wall needs.

1. Bonneville bench sands & gravels

   Common on the east benches from Bountiful to Draper. These soils drain well but erode quickly once disturbed, so cut faces are protected promptly and terrace surfaces are graded to keep runoff off the slope.

2. Expansive & collapsible clays and silts

   Found in North Salt Lake, Lehi, Herriman, and parts of the valley floor. Clay swells when wet and silt can collapse when saturated, so these sites get wider drainage zones, filter fabric everywhere native soil meets drain rock, and more conservative tier spacing.

3. Canyon cobble & debris-flow fans

   Near canyon mouths in Cottonwood Heights, Centerville, Alpine, and Farmington. Large buried cobbles slow excavation but make strong bearing; seasonal subsurface water often appears in cuts, so toe drains are sized to carry it.

4. Alpine clay-loam & bedrock

   In Park City, Heber City, and Wolf Creek Ranch, deep frost and heavy snowmelt dominate. Terraces there need free-draining backfill, careful outlet planning for spring runoff, and native stone that satisfies architectural review.

Access for Tight & Steep Lots

1. Narrow side yards

   Compact excavators and tracked carriers fit through openings of roughly 3 to 5 feet, though narrow access means smaller loads and more trips — the main reason access width moves the price.

2. Opening a route

   Temporarily removing a fence panel, gate, or strip of landscaping often saves more in labor than it costs to restore.

3. Staging & haul-out

   Boulders are delivered to a staging area and moved in one at a time; excavated spoils leave the same way.

4. Access as a feature

   A terrace project can create permanent access too — a ramp or path to a lower yard, or a bench wide enough for future equipment.

Making Terraces Usable

• Level lawn panels and play areas
• Patios, fire pits, and outdoor kitchens on compacted, stable benches
• Raised garden beds and planting pockets between tiers
• Boulder steps built into the walls for access between levels
• Irrigation sleeves and lighting conduit placed before backfill