Unit Prices
Wall Summary
Total Blocks
75
Courses
5
Face Area
60 sf
Cap Stones
15
Materials List
Estimated Total Cost
$1,227.74 – $2,127.74
12,800+ estimates calculated this month
Retaining Wall Cost & Design Guide
Per-square-foot costs, engineering requirements, and drainage details for retaining walls.
How Much Does a Retaining Wall Cost in 2026?
Retaining walls cost $20–$60 per square foot of wall face for standard residential installations, with costs increasing significantly for walls over 4 feet tall.
- Timber (landscape ties): $15–$25/sq ft face (shortest lifespan)
- Segmental block (Allan Block, Versa-Lok): $20–$40/sq ft face
- Natural stone: $25–$50/sq ft face
- Poured concrete: $30–$60/sq ft face
- Boulder walls: $25–$55/sq ft face
A typical 4-ft tall × 50-ft long wall (200 sq ft of face) costs $5,000–$12,000 in segmental block.
Key Takeaways
- Segmental block: $20–$40/sq ft of face
- Poured concrete: $30–$60/sq ft
- 4×50 ft wall: $5,000–$12,000 typical
When Is Engineering Required for Retaining Walls?
Walls over 4 feet tall generally require engineering and a building permit in most jurisdictions.
- Under 4 ft: Usually no permit needed (check local code)
- 4–6 ft: Permit required, may need basic engineering
- Over 6 ft: Structural engineering required ($1,500–$5,000 for design)
- Surcharge loads: If a driveway, building, or slope sits above the wall, engineering is needed regardless of height
An under-engineered retaining wall is a liability — failure can cause property damage, injury, and code violations costing far more than proper engineering.
Key Takeaways
- Over 4 ft: permit typically required
- Over 6 ft: structural engineering needed ($1,500–$5,000)
- Surcharge loads require engineering at any height
Critical Retaining Wall Drainage Requirements
Poor drainage is the #1 cause of retaining wall failure. Hydrostatic pressure from trapped water can push over even well-built walls.
- Gravel backfill: 12" of clean gravel behind the wall (not dirt)
- Drain pipe: 4" perforated pipe at the base, routed to daylight or a drainage point
- Filter fabric: Geotextile between soil and gravel to prevent fines from clogging drainage
- Weep holes: Every 4–8 ft along the wall face for block/concrete walls
Proper drainage adds $3–$8/sq ft to wall cost but is absolutely essential for long-term stability.
Key Takeaways
- Poor drainage = #1 wall failure cause
- 12" gravel backfill + drain pipe required
- Drainage adds $3–$8/sq ft (essential investment)
How to Use This Calculator
Enter wall dimensions
Input the total wall length in feet and the desired wall height. The calculator uses these to determine the number of courses and blocks per course.
Select your block size
Choose between standard 16x8 inch blocks or large 18x6 inch blocks. The block size determines how many you need and how many courses make up the wall height.
Adjust unit prices
Enter the cost per block, cap stone, gravel per ton, and labor rate per square foot. Prices vary significantly by region and block style.
Review materials and cost
See the total blocks, cap stones, base gravel, drainage gravel, and geogrid needs along with a full cost breakdown including labor.
Retaining Wall Formulas
Courses = Wall Height (in) / Block Height (in)
Blocks per Course = Wall Length (in) / Block Width (in)
Total Blocks = Blocks per Course x Courses
Cap Stones = Blocks per Course
Base Gravel = Length x 2 ft x 0.5 ft / 27 x 1.4 tons/yd
Drainage Gravel = Length x 1 ft x Height / 27 x 1.4 tons/ydWhere:
- Block Width
- = 16 inches (standard) or 18 inches (large)
- Block Height
- = 8 inches (standard) or 6 inches (large)
- 1.4
- = Tons per cubic yard of gravel
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Frequently Asked Questions
How many blocks do I need for a retaining wall?
How much does a retaining wall cost?
How much gravel do I need behind a retaining wall?
Do I need a permit for a retaining wall?
What is geogrid and when do I need it?
How long does a retaining wall last?
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