Find out how many blocks, how much gravel, and how much drain pipe and fabric you need for a block retaining wall.
0blocks
| Item | Amount |
|---|---|
| Courses (including buried) | |
| Blocks per course | |
| Cap blocks | |
| Base gravel | |
| Gravel behind wall | |
| Total gravel (10% extra) | |
| Drain pipe | |
| Landscape fabric |
A block retaining wall is built on a compacted gravel base, with the first course partly buried, a drain pipe at the bottom, and gravel packed behind the wall. The calculator estimates each of these from your wall size and block size.
Gravel is converted at about 1.4 tons per cubic yard and includes 10 percent extra for compaction.
Taller retaining walls need an engineered design. Many areas require a permit or an engineer for walls over about 4 feet, and walls that hold up slopes, driveways, or buildings may need it at any height. Taller segmental walls also need geogrid reinforcement, which this calculator does not estimate. Check local codes and follow your block maker's instructions.
The setback (lean) of each course, geogrid, block adhesive, soil removal, and any curves or corners. A wall with corners or steps needs extra blocks and planning.
With 12 x 4 inch blocks and one buried course, you need 10 courses of 20 blocks each, or about 210 blocks with 5 percent extra. Use the calculator for other block sizes.
It depends on the wall's height and length. A typical rule is a layer of clean gravel about 12 inches wide behind the wall, running its full height. The calculator adds this to the base gravel.
Most small walls use 4 to 6 inches of compacted gravel, and the trench should be about 12 inches wider than the block. Taller walls and soft soil need a deeper base.
It varies by area. Many places require a permit or engineered plans for walls taller than about 3 to 4 feet, and walls that support a slope above, a driveway, or a structure may need them at any height. Check with your local building department.
Usually yes. Perforated pipe carries water away from the wall's base, so pressure does not build up behind it. Slope the pipe to a place where water can leave.