How a Retaining Wall Is Actually Built: the Sequence, Course by Course

A retaining wall holds back a force every hour of every day for as long as it stands. Everything else in a backyard just sits there.

That is why the build sequence is rigid. Each step covers the one before it, and there is no going back without taking the wall apart.

Whether your wall needs an engineer, and what the permit threshold is, is a separate question answered in retaining walls in Temecula and Murrieta. This is what happens once that is settled.

Step 1 · Locate, and find out what is under you

Before anything moves: where is the property line, is there an easement, and what utilities cross the area. A wall built over an easement is a wall that may have to come out.

This is also when the soil question gets answered. On the clay through this valley, the lateral pressure a wall has to resist is higher than on granular soil, and clay swells when it gets wet. The soil decides the design.

Step 2 · Excavate, and go deeper than looks necessary

The trench has to be wide enough for the wall plus a drainage zone behind it, and deep enough that the base sits below finished grade — part of the wall is supposed to be buried.

Excavate to undisturbed soil. Fill that somebody placed years ago is not a foundation. If what you find is soft, wet or full of organics, it comes out and gets replaced with compacted structural material.

Step 3 · The leveling pad, which decides everything above it

Every error in the base course multiplies as the wall goes up. A base that is a quarter inch out over the first course is several inches out at the top.

The pad is compacted aggregate, screeded dead level, checked along the whole run and not just at the ends. For a segmental wall this pad is the foundation. For a reinforced masonry wall there is a poured concrete footing here instead, sized and reinforced to the design, with the vertical steel set into it before the concrete goes off.

Crews that build good walls spend a disproportionate share of the day on this step. That is the tell.

Step 4 · The first course

Set level in both directions, unit by unit, checked constantly. On a slope the base course steps down, and each step starts a new level run.

Most walls are built with a batter — a slight lean back into the slope. It is not cosmetic. Leaning into the retained soil buys the wall margin against the pressure pushing it out.

Step 5 · Build up, and put the drainage in as you go

This is the step where walls are won or lost, because the drainage is built into the wall rather than added to it.

1. A zone of clean, free-draining gravel directly behind the wall, full height.

2. Filter fabric between that gravel and the native soil, so fines do not migrate in and clog it.

3. A perforated collector pipe at the base of the gravel, laid with continuous fall to a real outfall.

4. Weep holes through the wall where the design uses them.

5. For a masonry wall, waterproofing or damp-proofing applied to the back face.

Skipping any of those is what produces a wall that weeps, efflorescences, bulges and eventually moves. The full argument is in waterproofing for retaining walls, and the drain itself follows the same rules as any subsurface drain — see French drains in Riverside County.

Step 6 · Backfill in lifts, and do not over-compact at the wall

Backfill goes in in layers, each one compacted before the next. Dumping the full height and running a compactor over the top compacts the top and leaves the rest to settle later, which shows up as a dip behind the wall and, under hardscape, as a crack.

But there is a counter-intuitive rule right at the wall: heavy compaction equipment used too close to the back of the wall can push it out. Near the wall you use hand equipment; the heavy plate stays back.

Step 7 · Geogrid, if the design calls for it

On a segmental wall above a modest height, the units alone are not the structure. Layers of geogrid are laid between courses and extend back into the compacted backfill, turning the wall and a wedge of soil behind it into one mass.

Two things have to be right: the vertical spacing between grid layers, and how far each layer extends into the backfill. Both come from the engineering, not from judgment on site. Grid cut short is the most common hidden defect in segmental walls.

Step 8 · Cap, finish grade, and send the water somewhere

Cap units get set, usually adhered. Then the grade above the wall is finished so surface water does not run straight in behind it — which would defeat the drainage you just built.

And the collector pipe has to actually discharge somewhere legal. A drain with no outfall is a buried reservoir against your wall.

What to watch for if you are not building it yourself

• How long did they spend on the base? If the answer is 'not long', that is the answer.

• Is there clean gravel going in behind the wall, and fabric separating it from the soil?

• Is there a pipe at the bottom of that gravel, and does it fall toward somewhere?

• Is the backfill going in in layers?

• If it is a segmental wall over a few feet, is geogrid going in, and how far back does it run?

Five questions. Every one of them is invisible the day the wall is finished.

A retaining wall is the one backyard element where a shortcut is a safety issue rather than a cosmetic one. Book a free 15-minute call or call (323) 707-4979 and describe the grade change and what sits above it.

See how the work actually goes together. X Plan Nation is our construction channel on YouTube — the same licensed crew as The Ultimate Pro, filmed on real job sites, with the reasoning behind the decisions you just read about.

The Ultimate Pro, Inc. · California contractor license 831700 · Class B general building · 18481 Grand Avenue, Lake Elsinore, CA 92530 · Serving the Inland Empire — Riverside County, Los Angeles County, Orange County and San Bernardino County — since 1996.