Calculation Results
About This Calculator
Calculate segmental concrete retaining wall block counts (SRW Allan Block / Keystone), course layers, buried base block row, gravel drainage backfill tons, and capstones.
Frequently Asked Questions
Why must the bottom course of a retaining wall be buried?
Burying the first row of blocks (at least 6 inches, or 10% of total wall height) locks the base into the compacted gravel footing, preventing the tremendous lateral earth pressure from kicking the bottom of the wall outward.
Why is a 12-inch drainage gravel zone required behind retaining walls?
Hydrostatic water pressure is the #1 cause of retaining wall collapse. A 12-inch column of clean, washed angular gravel behind the blocks allows water to drop straight down into the perforated drain pipe rather than saturating and pushing against the wall face.
When is geogrid reinforcement mandatory in retaining walls?
Most municipal building codes mandate geogrid soil reinforcement layers and stamped civil engineering plans for any retaining wall with an exposed height exceeding 4 feet (48 inches).
What should be used for the leveling pad footing under retaining wall blocks?
Never pour an unreinforced concrete footing or place blocks on raw soil. Use a 6-inch compacted bed of crushed aggregate base (dense-grade road base or 3/4" minus) compacted in 2-inch lifts.