Block wall materials for 80 ft at 12 courses, rebar every 24″
| Blocks (with 5% breakage) | 756blocks |
|---|---|
| Blocks (exact)1.125 per ft² including joints | 720blocks |
| Wall area80 ft × 8 ft | 640ft² |
| Wall height12 courses at 8″ | 8ft |
| Mortar (Type S, 70 lb)3 bags per 100 blocks at ⅜″ joints | 22bags |
| Masonry sandif mixing from bagged cement and lime instead | 2.93yd³ |
| Vertical rebar (#4 @ 24″)390 linear ft including 18″ into the footing | 41bars |
| Grout for filled cells214 × 80 lb bags — only the cells with steel in them | 127.9ft³ |
| Footing16″ × 8″ × 80 ft — twice the wall thickness | 2.63yd³ |
| Engineering8 ft is over the 4 ft threshold | Required |
Notes
- 1.125 blocks per square foot is the number, and it already includes the ⅜″ mortar joints. A "8×8×16" block is 7⅝ × 7⅝ × 15⅝ actual — the missing ⅜″ is the joint, which is why nominal dimensions divide so cleanly into wall areas.
- Grout goes only in the cells that have steel in them — 41 cells here, 127.9 ft³. Solid-grouting the whole wall is a different job with several times the material and a footing sized for several times the load.
- At 8 ft this is past the point where most jurisdictions want an engineered design and a permit — universally so if it retains soil. Soil pushes sideways with a force that grows with the square of the height, and a wall sized by rule of thumb fails by overturning, not by crushing.
- The footing decides whether the wall lasts. 16″ × 8″ is the usual rule of twice the wall thickness, below the frost line, on undisturbed soil. Block laid on a footing that heaves cracks along the mortar joints, and there is no repair short of rebuilding.
- Drainage behind any wall holding back soil is not optional: gravel backfill, a perforated pipe at the base and weep holes. Water pressure behind a wall is a larger force than the soil itself, and it is what actually pushes walls over.
Blocks
80 ft × 12 courses is 8 ft high and 640 ft² of wall — 756 blocks with 5% for breakage and cuts.
The number to remember is 1.125 blocks per square foot, and it already includes the ⅜″ mortar joints. A block sold as 8×8×16 actually measures 7⅝ × 7⅝ × 15⅝; the missing ⅜″ is the joint, which is why nominal sizes divide so neatly into wall areas.
Mortar
22 bags of Type S at ⅜″ joints, or 2.93 yd³ of masonry sand if you are mixing from cement and lime instead.
Steel and grout
41 vertical bars, 390 linear ft including 18″ of anchorage into the footing, and 127.9 ft³ of grout — 214 bags.
Grout goes only in the cells that have steel in them. Solid-grouting the whole wall is a different job with several times the material and a footing sized for several times the load.
The footing decides whether it lasts
2.63 yd³ at 16″ × 8″, below the frost line, on undisturbed soil. Block laid on a footing that heaves cracks along the mortar joints, and there is no repair short of taking it down.
Before you start
Anything over 4 ft, and anything at all that retains soil, needs an engineered design and a permit almost everywhere. Soil pushes sideways with a force that grows with the square of the height, and walls sized by rule of thumb fail by tipping over rather than by crushing.
Drainage behind a retaining wall is not optional either: gravel backfill, perforated pipe at the base, weep holes. Water pressure behind a wall is a bigger force than the soil, and it is what actually pushes walls over.
Nearby sizes
- Block wall materials for 76 ft at 12 courses, rebar every 24″
- Block wall materials for 84 ft at 12 courses, rebar every 24″
- Block wall materials for 72 ft at 12 courses, rebar every 24″
- Block wall materials for 88 ft at 12 courses, rebar every 24″
- Block wall materials for 80 ft at 11 courses, rebar every 24″
- Block wall materials for 80 ft at 10 courses, rebar every 24″
Read more
- How Many Blocks for a Wall: The 1.125 Rule and What It Leaves OutA standard block covers exactly 0.889 square feet of wall including its mortar joint, which is why one number does all the work — and why the block count is the least of your problems.
- Bags or a Truck — The Crossover Is About One Cubic YardThe arithmetic is not really about price. It is about how long a slab can sit half-poured before the joint between the halves becomes permanent.
- Rebar in a Slab — Spacing, Cover, and Why Position Matters MoreRebar laid on the ground and left there does nothing. It has to be held up into the concrete, and that is the step that gets skipped.
- Concrete Slab Cost by State — 400 ft², All 51The figures price a 4-inch slab on grade. A driveway wants six inches and rebar, and that is not a small adjustment.