Retaining Walls

What is a Retaining Wall

Retaining walls are structural systems that hold back soil and shape elevation. They’re what allow a flat patio to exist where there used to be a slope.

Sometimes they’re small transitions. Sometimes they’re engineered structures managing real load. Either way, they’re not decorative borders. If they fail, the space around them fails too. They affect drainage, grading, and what can be built above or below them.

Design Considerations

The first question is load. What is the wall supporting — and how much of it? That determines height, reinforcement, and whether engineering is required.

Then we look at placement. Is it creating usable space above? Supporting a patio edge? Managing drainage behind it? Walls often dictate where stairs land, where lighting gets integrated, and how planting transitions happen.

Visually, the scale has to feel intentional. A wall that’s structurally correct but proportionally wrong still feels off.

How It's Built

Retaining walls begin with excavation and base preparation. For segmental retaining wall (SRW) systems, the wall itself does not extend below the frost line like a poured footing would. Performance depends on proper base prep, reinforcement, and drainage. Most wall failures we see trace back to inadequate base depth or improper backfill — not the block itself.

We excavate and install a compacted aggregate base to create a stable leveling pad before the first course is set. That first row must be perfectly level. Any deviation compounds as the wall rises.

Engineering thresholds vary by municipality. In many of the areas we build, walls over 6 feet in height (measured from the bottom of the base) require engineering. In more densely populated municipalities, that threshold is often 4 feet. The reason isn’t arbitrary — it’s tied to population density and liability. When walls are near homes, property lines, or public infrastructure, the structural consequences matter more.

When height or load conditions warrant it, we follow engineered specifications exactly. Structural walls incorporate geogrid reinforcement extending back into the retained soil. The grid ties the wall mass into the surrounding earth, creating a reinforced soil system rather than a freestanding stack of block.

Behind the wall, we install clean ¾” rock backfill — not native soil pushed back into place. That stone creates a drainage column leading down to a perforated drain tile installed at the base of the wall. The drain line is routed to daylight or an approved discharge point. Water pressure is the number one cause of retaining wall failure, so drainage is treated as structural, not optional.

Caps are cut to fit and secured with exterior-rated adhesive. Transitions into patios, steps, or adjacent grade are coordinated so loads are distributed properly and the wall integrates into the broader hardscape system without creating pressure points.

Retaining walls aren’t decorative borders. They’re structural systems. When base prep, reinforcement, and drainage are handled correctly, they quietly hold everything else in place.

Pricing Factors

Small structural retaining walls typically begin around $15,000–$25,000 depending on height and length.

Mid-sized retaining walls that involve grade transitions, longer runs, or reinforced construction commonly range from $25,000–$60,000 depending on soil conditions and structural requirements.

Larger engineered retaining wall systems — especially those exceeding typical height thresholds, supporting driveways or structures, or requiring geogrid reinforcement and advanced drainage systems — often fall between $60,000–$150,000+ depending on site conditions and engineering scope.

Engineered walls increase in cost not just because of visible height, but because of the volume of excavation, structural aggregate, geogrid reinforcement, drainage components, and backfill effort required behind the wall. A significant portion of the structural investment occurs below grade and isn’t visible once the project is complete.

Primary cost drivers include wall height, total linear footage, soil conditions, reinforcement depth, drainage design, access constraints, and whether engineering or permitting is required.