Retaining Wall Build Sheet
Block counts on one side, the things that actually hold a wall up on the other. The second list is the important one.
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The wall
- Location
- Date
- Wall length
- Exposed height
- Block size
- Blocks per course
- Courses
- TOTAL BLOCKS
- Cap blocks
- Permit needed?
Sections — measure each straight run separately
| Section | Length | Exposed height | Courses | Blocks |
|---|---|---|---|---|
The arithmetic
- Blocks per course
- wall length in inches / block length, rounded UP
- Courses
- exposed height / block height, rounded UP, + 1 buried
- Total blocks
- blocks per course x courses
- Caps
- one more course's worth
- ⚠ Rounding
- applies to EVERY course, not once
- ⚠ Buried course
- standard practice — 25% more on a 4-course wall
- Not counted
- base gravel, drainage, geogrid, adhesive
Before you buy a single block
- PERMIT and engineering checked — commonly required above 3-4 ft
- Slope, driveway or structure above the wall? The threshold drops
- UTILITIES LOCATED before any digging
- Property line confirmed
- Compacted gravel base planned and its depth decided
- DRAINAGE designed — aggregate and pipe behind the wall
- Where the water goes at the end of the pipe, decided
- Geogrid specified if the design calls for it
- Setback per course checked against where the face should finish
- Wall length adjusted to whole blocks if the design allows
Drainage is what fails walls, not blocks
A retaining wall almost never fails because someone bought too few blocks. It fails because water collected behind it with nowhere to go, and saturated soil pushes far harder than dry soil. The aggregate and the pipe are not optional extras that a tight budget can drop — they are the part doing the work that the blocks get credit for.
Height is a safety question, not an arithmetic one
This sheet counts blocks. It says nothing about whether your wall will stand, and no calculator can. Above roughly three or four feet most places require an engineered design and a permit, and less than that if anything is surcharging the wall from above. A retaining wall holds back a great deal of weight and fails suddenly rather than gradually.