Retaining wall material is usually chosen by looks. It should be chosen by height, by what the wall carries and by how water leaves the soil behind it. This picker works through those three in order and only then gets to price.
Measure from the bottom of the footing to the top of the wall, because that is what codes and costs key on. All walls hold soil at two levels and resist sideways earth pressure, but they do it differently: gravity walls with mass, cantilever walls with a footing and reinforcement, anchored walls with something driven or grouted into the ground behind (types of retaining wall). A cantilever wall suits heights above about 4 to 6 feet or a heavy load on top.
Taller reinforced-soil walls are engineered structures. The US Federal Highway Administration publishes GEC 11, its reference manual for the design and construction of mechanically stabilized earth walls and reinforced soil slopes, which gives a sense of how much design sits behind a tall wall.
| Material | Installed cost per sq ft | Fits best | Watch for |
|---|---|---|---|
| Segmental block | $15–$35 | Most residential walls | Needs drainage like any wall |
| Poured concrete | $25–$60 | Tall walls, walls carrying a driveway, pool or structure | Formwork and curing time |
| Timber | $10–$25 | Low garden edges | Shortest life, roughly 15–25 years in wet soil |
| Gabion | $20–$40 | Free-draining, naturalistic sites | Wire corrosion; 25–50 years |
| Boulder | $20–$45 | Natural stone look, seepage slopes, good machine access | Access drives the price |
A boulder wall is a gravity wall of large stone on a compacted base, battered back into the slope and drained through its open joints. The stone is typically $120 to $350 per ton delivered, and a 160 square foot wall runs about $3,200 to $7,200 (boulder wall cost).
The failure pattern is almost always water, as timber retaining wall problems explains; pressure-treated lumber rated for ground contact lasts years longer than untreated wood.
Excavating for a footing or a drain is where people get hurt. OSHA notes that trench collapses, or cave-ins, pose the greatest risk to workers in excavation, and describes sloping, benching and shoring based on soil analysis. If the cut is deep, that is a job for a contractor with the right equipment. Locate buried utilities before any digging.