Retaining Wall Design Guidelines
| Wall Height | Batter (Setback) | Base Burial | Permit Needed |
|---|---|---|---|
| Under 2 ft | None required | 4–6 inches | Rarely |
| 2–4 ft | 1" per foot | 6–8 inches | Sometimes |
| 4–6 ft | 1" per foot | 8–12 inches | Usually |
| Over 6 ft | Engineer required | 12"+ / footing | Always |
Frequently Asked Questions
How many retaining wall blocks do I need?+
Divide wall height (in inches) by block height, then multiply by blocks per row (wall length in inches ÷ block width). For a 40-ft wall at 24 inches using 4×12 blocks: (24÷4) × (480÷12) = 6 rows × 40 blocks = 240 blocks.
How deep should a retaining wall base be?+
Bury the first course 6 inches below grade for small walls (under 3 ft). For larger walls, bury one block height (4–6 inches) per foot of wall height, up to 12 inches. Always set on a 6-inch compacted gravel base.
Do I need a permit for a retaining wall?+
Most municipalities require permits for walls over 4 feet tall measured from the bottom of the footing. Walls near property lines or holding back slopes with buildings above often need permits at lower heights. Always check local codes.
How much does a retaining wall cost?+
DIY interlocking block walls run $8–20 per square foot of wall face, including materials. Professional installation adds $15–35/sq ft in labor. A 40-ft long, 2-ft tall wall (80 sq ft) typically costs $640–$1,600 in DIY materials.