Why most retaining walls fail, and how we build ours
A wall that leans doesn't fail because the concrete was weak. It fails because water got behind it. Tear one out and the story is always the same: dense clay packed right against the back of the wall, no gravel, no drain pipe, and a footing that's too shallow or missing altogether. When that clay soaks up a wet spring, it swells and pushes. Water that can't escape adds pressure on top of that. The wall tilts a little more every year, and then one winter a section cracks through.
So we build the wall and the drainage together. That means a footing dug below frost and sized for the wall's height, a rebar cage tied into the footing, and a poured wall with weep holes at the base. Behind it goes drain rock and a perforated pipe that carries water away to daylight or a safe outlet, so it never builds up against the concrete.
Typical pricing runs $40 to $75 per sq ft of wall face. A 30 ft long, 3 ft tall wall (90 sq ft of face) usually lands between $3,600 to $6,750. Taller walls, curves, and tough access change that, so we price each one after we see the slope. These walls are part of our residential concrete work, alongside the slabs and patios they often protect.
Is your wall a problem now, or can it wait?
Walls give warning before they go. Here's what we look for when we walk a property.
Call soon if you see
- A wall that leans out from the bottom, or a top edge that has moved since last year
- Horizontal cracks, or stair-step cracks that keep growing
- Bulges in the face, or chunks pushed out between cracks
- Soil washing out from the base or from under the footing
- Water running down the face instead of out of the weep holes
Usually safe to watch
- Hairline vertical cracks that have not changed in a year or more
- Light staining or mineral deposits at the weep holes
- Surface wear from weather on an otherwise plumb wall
- A short, low wall holding back a small planter bed
Why retaining walls lean, crack, and fail
Hydrostatic pressure
Water that collects behind a wall presses on it like a heavy liquid. Soil that's saturated can push far harder than soil that's dry. This is the leading cause of failed walls, and the fix is always drainage: gravel behind the wall, a perforated pipe at the bottom, and weep holes that stay open.
Clay swelling
Aurora clay expands when it gets wet and shrinks as it dries. Packed against a wall, it pushes on every wet cycle and then pulls away, which loosens everything. Using free-draining rock against the wall, instead of the clay we dug out, cuts that pressure.
No drainage at all
A lot of older walls have nothing behind them but dirt. They stand for a few years, then start to tip. Adding drainage later usually means digging up the whole backfill, and by then the wall is often bent past saving. It's cheaper to build the drainage the first time.
Weak or shallow footings
The footing keeps the wall from sliding or tipping. If it's too narrow or sits above the frost line, the whole thing shifts every winter. We size the footing to the wall and dig it deep enough to stay put.
Fix it or rebuild it
A wall that is plumb, with one or two tight cracks, can sometimes be saved. Fixing the drainage behind it and sealing the cracks may be all it needs. A wall that has already tilted or bulged won't straighten itself, and patching the face doesn't stop the soil pushing from behind. In that case we take it down, rebuild the footing, and pour new.
If the surface has just worn down and the wall is still solid, concrete resurfacing can tidy up the face. Cracks that stay narrow and don't move can be filled using concrete crack repair.
Walls that need a permit or an engineer
Under the International Residential Code that most Colorado cities adopt, walls over 4 feet, measured from the bottom of the footing, typically need a permit and often an engineered design. So do walls holding back a surcharge, like a driveway or a slope above. Confirm requirements with the City of Aurora Building Division before you plan the wall.
How we build a poured concrete retaining wall
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Walk the slope and plan the drainage
We look at what the wall holds back, where the water comes from, and where it can go. You get a written price and a plan for the drain outlet before anything is scheduled.
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Dig and pour the footing
We excavate to firm ground and below frost depth, set the footing forms, and tie in the rebar that will rise up into the wall. The footing is poured first and given time to set.
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Form and pour the wall
Wall forms go up on the footing with a rebar cage inside. We pour 4,000 PSI air-entrained concrete, vibrate it into every corner, and leave weep holes at the bottom. The face is finished however you like.
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Drain rock, pipe, and backfill
Once the wall has cured, we lay a perforated pipe along the base, cover it with drain rock, and backfill. The pipe is sloped to carry water out and away from the wall.
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Cure and finish
We keep the concrete damp while it cures. Backfilling is held off until it has gained strength, and heavy loads should stay off the top soil for a few weeks.
What affects the price of a retaining wall
Most walls land between $40 to $75 per sq ft of wall face. Here's what moves a job up or down that range.
- Height and length
Price is per square foot of wall face, so height counts as much as length. Taller walls need bigger footings and more steel, and the cost rises faster than the height.
- Site prep
Digging into a hillside, working around trees, or removing existing blocks or timbers adds labor. Soft ground may need extra base under the footing.
- Removing the old wall
Demo and haul-off of a failed wall runs about $3 to $7 per sq ft for concrete, and more if it's stacked block or timber with lots of backfill to move.
- Finish type
A plain formed face is the base price. Form liners for a stone or board pattern, color, and caps cost more.
- Access
If the truck can reach the forms, the pour is simple. A backyard with a narrow gate may need a pump or wheelbarrows, which adds time.
- Reinforcement and engineering
Taller walls, or walls holding back a driveway or slope, need heavier steel and sometimes engineered plans. Stamped drawings are a separate cost from the wall.
Building a wall through Aurora’s seasons
Winter
Footings can't be poured on frozen ground, and fresh concrete needs protection from freezing. Most wall work waits for spring unless there's a mild stretch.
Spring
Spring is the busy season, but wet clay slows excavation and a wall dug into soaked soil is harder to build well. We wait for the ground to be workable.
Summer
Summer is a strong window for walls. Dry soil digs cleanly, and we pour early in the day so the heat and wind don't pull water out of the concrete before it cures.
Fall
Fall works if we start early. Walls should be backfilled with drain rock and have clear outlets before the freeze, so melting snow has somewhere to go.
Aurora soil, HOAs, and permits for retaining walls
Expansive clay soil
Much of Aurora sits on clay that swells and shrinks. It's the main reason walls here need real footings and free-draining backfill. We never use that clay as backfill directly against the wall.
Deicing salt
Walls beside driveways and sidewalks take salt spray every winter. Air-entrained mix and a penetrating sealer help the face last. Keep deicers off the top of a new wall for its first winter.
HOA approval
Many Aurora neighborhoods require architectural approval for walls, especially along property lines or visible from the street. Get it in writing first. We can supply the specs your HOA asks for.
City of Aurora permits
Taller walls, and walls holding back a driveway or slope, typically need a permit and often an engineered design. Confirm with the City of Aurora Building Division for your address. Steps or a patio at the base of the wall can add their own requirements, so look at our concrete patios and concrete steps pages if they are part of the plan.
Retaining Walls FAQs
How much does a concrete retaining wall cost in Aurora?
Most walls run $40 to $75 per sq ft of wall face of wall face. A 30 ft long, 3 ft tall wall (90 sq ft of face) is typically $3,600 to $6,750. Height, demo, and engineering add to that.
Do I need a permit for a retaining wall?
Often, yes. Under the International Residential Code most Colorado cities adopt, walls over 4 feet from the bottom of the footing, or walls holding back a driveway or slope, typically need a permit and often an engineered design. Confirm with the City of Aurora Building Division.
Why is my retaining wall leaning?
Usually water. Poor drainage lets pressure build behind the wall, and Aurora clay swells and pushes when it's wet. A weak or shallow footing makes it worse.
What are weep holes for?
They let water leave from behind the wall. Without them, pressure builds up and the wall can lean or crack. Keep them clear of dirt and mulch.
Can a leaning wall be straightened?
Rarely. Once a poured wall has tilted or bulged, it needs to be rebuilt with a proper footing and drainage. Small cracks in a plumb wall can often be sealed.
How long does a poured retaining wall last?
With a good footing, steel, and drainage that stays open, decades. Most failures come from water, not from the concrete itself.