Retaining walls are the line item people underestimate. Half the cost of a well-built West County wall is buried behind it: drainage stone, outlet, compacted backfill and geogrid.
| Scope | West County installed range |
|---|---|
| Segmental block, under 4 ft exposed | $45 - $75 per face sq ft |
| Segmental block, over 4 ft (engineered, geogrid) | $70 - $130 per face sq ft |
| Boulder wall, under 3 ft | $40 - $70 per face sq ft |
| Engineering and stamped drawings | $900 - $3,500 |
| Drainage stone, pipe and outlet | $18 - $40 per linear ft |
| Cap course, adhered | $22 - $45 per linear ft |
| Partial rebuild of a leaning wall (top courses) | $60 - $110 per face sq ft |
What does a retaining wall cost in West County?
Straight answerSegmental block walls in West County run roughly $45 to $75 per face square foot under four feet, and $70 to $130 per face square foot once the wall is tall enough to require geogrid reinforcement and an engineered design.
What is a face square foot and why is the wall quoted that way?
Straight answerFace square footage is exposed height times length, so a 30-foot wall averaging 4 feet tall is 120 face square feet. Walls are quoted that way because cost tracks the buried structure behind the face, not the footprint on your lawn.
When does a West County retaining wall need an engineer?
Straight answerCommonly at four feet of exposed height, and lower if there is a surcharge above the wall such as a driveway, pool or slope. Several West County municipalities require a stamped design and a permit at that threshold, so confirm the jurisdiction before design is final.
Why do so many older West County walls lean?
Straight answerAlmost always no drainage stone, no outlet and no geogrid. Clay behind a wall holds water, water adds weight, and the wall rotates forward. A leaning wall is a drainage failure wearing a masonry costume.
Can a leaning wall be repaired or does it need a rebuild?
Straight answerIf the block is intact and movement is minor, a partial rebuild of the top courses with new drainage and geogrid can save it. Once the base course has shifted, a full rebuild is cheaper than chasing it, because the failure is under the ground, not on the face.
Boulder wall, segmental block or poured concrete?
Straight answerSegmental block dominates West County for cost, permitting familiarity and repairability. Boulder walls suit naturalistic slopes and can be cheaper at low heights. Poured concrete makes sense mainly when it doubles as structure for something else.
Ask for the buried half in writing
Drainage stone, outlet location, geogrid layers and backfill compaction. A builder who will not put those on the bid is quoting a facade.
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