Poured Retaining Wall Calculator

About the Poured Retaining Wall Calculator

Poured concrete retaining walls are the strongest option for retaining soil, suitable for walls from 3 feet to over 20 feet tall. They consist of a footing (base) and a stem (vertical wall), both reinforced with steel rebar. Professional engineering is typically required for walls over 4 feet.

This calculator estimates the concrete volume for both the footing and stem, the rebar requirements, and the formwork area. The standard design uses a footing width of 50–70% of the wall height and a footing thickness of 8–12 inches, with a stem thickness of 8–12 inches tapering for taller walls.

Whether you're building a heavy-duty retaining wall for a hillside, driveway, or commercial site, this calculator provides the concrete yard and rebar estimates you need for ordering and cost planning.

When This Page Helps

Poured concrete walls are expensive and require precise material estimates. Over-ordering concrete is costly, and under-ordering means partial pours and cold joints. This calculator ensures accurate quantities for a continuous, high-quality pour.

How to Use the Inputs

1. Enter the wall length in feet.
2. Enter the total wall height (exposed + buried).
3. Set the stem (wall) thickness.
4. Enter the footing width and thickness.
5. Review concrete volume in cubic yards.
6. Check rebar and formwork estimates.

Example Calculation

Tips & Best Practices

• Always have a structural engineer design walls over 4 feet tall.
• Use 3,000–4,000 PSI concrete for retaining walls.
• Rebar spacing is typically 12–18 inches on center, both ways.
• Form both sides of the stem for a clean finish.
• Include weep holes or drain pipes for hydrostatic pressure relief.
• Order 10% extra concrete to account for waste and form bulging.

Anatomy of a Poured Retaining Wall

A poured retaining wall has two main parts: the footing (a horizontal base spreading the load) and the stem (the vertical wall). The footing is poured first, with rebar dowels left protruding for the stem. After the footing cures, forms are set and the stem is poured.

Footing Design Basics

The footing resists overturning and sliding forces. Its width is proportional to wall height — typically 50–70% of the total height. The key (a groove cast in the footing top) helps resist sliding. Rebar ties the footing and stem together as a monolithic unit.

Drainage Is Critical

Hydrostatic pressure (water buildup behind the wall) is the #1 cause of retaining wall failure. Install weep holes every 6–8 feet at the base, or run a continuous perforated drain pipe behind the footing. Backfill with crushed gravel to promote drainage.

Formwork Considerations

Both sides of the stem require forms. Use plywood or steel forms braced to resist the pressure of wet concrete (150 pcf). Form ties maintain wall thickness. Strip forms after 24–48 hours and begin moist curing immediately.

Frequently Asked Questions

• How thick should a poured retaining wall be?

  Stem walls are typically 8 inches thick for walls up to 4 feet and 10–12 inches for taller walls. Engineers may taper the stem from thick at the base to thin at the top. The footing is usually 8–12 inches thick and 50–70% as wide as the wall is tall.

• How much rebar is needed?

  Typical residential retaining walls use #4 or #5 rebar at 12–18 inches on center in both directions. The stem needs vertical and horizontal bars on the tension side, plus the footing needs rebar running lengthwise and across its width.

• What is the footing size rule of thumb?

  Footing width = 50–70% of wall height. Footing thickness = 8–12 inches. The toe (front) extends 1/3 of footing width, and the heel (back) extends 2/3. These are rough guidelines — engineered walls vary.

• How much does a poured retaining wall cost?

  Poured concrete retaining walls cost $25–$60 per face square foot installed, including forming, rebar, concrete, and labor. A 40 ft × 6 ft wall costs roughly $6,000–$14,400. DIY can save 40–50% but requires forming experience.

• Do I need a permit?

  Yes, almost all poured retaining walls require a building permit, especially those over 4 feet. You'll need engineered drawings showing footing design, rebar placement, and drainage plan. Inspections are required at footing and rebar stages.

• How long does it take to cure?

  Concrete reaches 70% strength in 7 days and full design strength (28 days) in about a month. Don't backfill against the wall for at least 7 days. Keep concrete moist during the first week for proper curing.