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Blocks, caps, mortar, rebar, grout and footing for a CMU fence wall.
With these inputs:
| Result | Value |
|---|---|
| Estimated materials | $1,657.43 |
| 8x8x16 blocks | 284 |
| Courses × blocks per course | 9 × 30 |
| Cap blocks | 30 |
| Type S mortar (80 lb bags) | 24 |
| Vertical bars | 11 |
| #4 rebar to buy (20 ft pieces) | 9 |
| Grout (80 lb bags) | 34 |
| Footing concrete (yd³) | 1.98 |
| Cost per linear foot | $41.44 |
A standard concrete masonry unit is 16 inches long and 8 inches high including the 3/8 inch mortar joint, so every course is the length divided by 16 inches and the number of courses is the height divided by 8 inches. That works out at 1.125 blocks per square foot. One 80 lb bag of Type S mortar lays up to about 13 blocks (QUIKRETE Mason Mix data sheet). Vertical #4 bars go in a grouted cell at your spacing plus one at the end, and the top course is a bond beam with two continuous bars filled solid. The footing is twice the wall width (16 inches) by your depth.
Blocks = ⌈length × 12 ÷ 16⌉ × ⌈height × 12 ÷ 8⌉ × (1 + waste) · Mortar bags = (blocks + caps) ÷ 13 · Vertical bars = ⌊length × 12 ÷ spacing⌋ + 1 · Grout = bars × courses × 0.115 cu ft + bond beam × 0.3 cu ft · Footing = length × 16/12 × depth ÷ 27
Multiply the wall length by its height in square feet and multiply by 1.125, because a standard 8x8x16 block covers 0.889 sq ft including the mortar joint. A 40 ft by 6 ft wall is 240 sq ft, so 270 blocks, plus about 5% for cuts and breakage.
One 80 lb bag of Type S mortar lays up to about 13 standard 8x8x16 blocks (QUIKRETE's data sheet figure), so a 270-block wall with 30 caps needs about 24 bags. Premixed bags are easiest for small walls; for bigger ones, masonry cement and sand mixed on site is cheaper.
Materials for a plain 6 ft CMU wall typically run $25 to $45 per linear foot with footing, rebar and grout; installed by a mason, $60 to $140 per foot depending on region, height and finish. Use your local block and concrete prices in the calculator for your own figure.
Almost always for a freestanding wall over about 3 ft. Vertical #4 bars in grouted cells every 32 to 48 inches, plus a bond beam at the top, are typical; many jurisdictions publish a standard design for garden walls. Walls over 6 ft or in seismic areas need an engineered design.
At least 12 inches deep and 16 inches wide for a typical 8 inch wall up to 6 ft, and below the frost line in cold climates. Local code governs — the permit office will state the minimum.
Most blocks sold today are concrete masonry units made with sand and gravel; true cinder blocks used coal ash and are rarely made now. People use both names for the same 8x8x16 hollow block.
Many towns require one for any masonry wall over 3 or 4 ft, and for any wall retaining soil. Check the fence height limits on your boundary as well.
Only the cells with rebar and the top bond beam are usually filled. One filled cell in an 8 inch block takes about 0.115 cu ft per course, and a solid bond-beam block about 0.3 cu ft. An 80 lb bag yields about 0.6 cu ft.
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