How many blocks for a 100 ft long, 2 ft high retaining wall?
A 100 ft wall showing 2 ft above grade takes 735 standard 12 × 4 in blocks in 7 courses, one of them buried, plus 105 cap units. Under and behind it you need 3.23 cubic yards of base gravel (4.8 tons), 9.51 cubic yards of drainage stone, 104 ft of perforated pipe, and 533 sq ft of fabric. In larger 18 × 8 in blocks the wall takes 282 blocks.
Blocks for a 100 ft × 2 ft wall by block size
| Block | Blocks (5% extra) | Courses | Caps | Block cost, typical |
|---|---|---|---|---|
| 12 × 4 in standard | 735 | 7 | 105 | $2,058 to $3,344 |
| 16 × 6 in | 394 | 5 | 79 | $1,891 to $3,073 |
| 18 × 8 in large | 282 | 4 | 71 | $2,030 to $3,299 |
| 8 × 4 in garden wall | 1,103 | 7 | 158 | $2,206 to $3,585 |
Each count includes one buried course below grade and 5 percent for cuts. Base gravel, drainage stone, pipe, and fabric are the same for every block.
Change the numbers
The calculator below is preset for this size. Adjust anything and the results update instantly.
Base and drainage for a 100 ft wall
- Trench: 10 in deep and about 19 in wide along the full 100 ft, roughly 4.9 cubic yards of digging.
- Base gravel: 3.23 cubic yards of 3/4 in minus, compacted in lifts, about 4.8 tons. See the gravel calculator to price it.
- Drainage stone: 9.51 cubic yards of clean 3/4 in stone for a 12 in column behind the blocks, about 14.3 tons.
- Drain pipe: 104 ft of 4 in perforated pipe with a sock, sloped to daylight at one or both ends.
- Fabric: 533 sq ft of non-woven landscape fabric to separate stone from soil.
- Adhesive: 10 tubes of construction adhesive for the caps and top course.
At this height no geogrid is normally needed, but keep the 12 in of drainage stone and the buried course; they matter more than anything else.
What a 100 ft × 2 ft block wall costs
Materials run about $3,272 to $5,154: standard blocks at $2.80 to $4.50 each, caps at $3 to $5, gravel and stone at $45 to $65 a ton, plus pipe and fabric. Larger blocks cost more per piece but fewer are needed, so the total lands in a similar range. Installed by a landscaper, segmental block walls typically price at $20 to $40 per square foot of wall face, or $4,000 to $8,000 for this 200 square foot wall. The blocks alone weigh about 11.0 tons, so plan on delivery.
Common questions
How many retaining wall blocks for 100 feet?
735 standard 12 × 4 in blocks for a wall 2 ft above grade, 394 of the 16 × 6 in size, or 282 of 18 × 8 in blocks, each including a buried course and 5 percent extra.
How much gravel for a 100 ft retaining wall?
3.23 cubic yards for a 6 in compacted base plus 9.51 cubic yards of clean stone behind the wall, about 19.1 tons in total.
Do I need a permit for a 2 ft retaining wall?
Usually not for a wall under 3 to 4 ft that is not holding up a driveway or structure, but check locally. Rules vary by city, so call the building department before you dig.