How Many Concrete Blocks to Build a 3000 Square Foot House?
Block to buy
2,079 block
220 ft of exterior wall around a 3000 sq ft single story, typed 50 by 60, 12 courses of 8 in block, 8 ft tall, openings not deducted, 5 % waste.
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How that number is worked out
These are the figures this page was built with and every line the calculator produces from them. Change anything above and all of it moves.
- Wall length220 ft
- Wall height8 ft
- Openings to deduct0 sq ft
- Block width, nominal8 in
- Grouted cellsEvery 48 in
- Waste allowance5 %
Block to buy2,079 block
| Net wall area | 1,760 sq ft |
|---|---|
| Block before waste | 1,9801.125 per sq ft |
| Courses | 12165 block per course |
| Mortar to buy | 91.4 cu ft |
| Mortar mix, 80 lb bags | 15313 block per bag |
| Cells to grout | 56 |
| Grout | 84 cu ft3.11 cu yd |
| Vertical rebar | 560 ft56 bars at 48 in on center, wall height plus a 2 ft lap |
| Joint reinforcement | 1,320 ftevery other course |
The material list this produces
| Block | 2,079 |
|---|---|
| Mortar mix, 80 lb bags | 153 |
| Grout, cu yd | 3 |
| Vertical rebar, ft | 560 |
| Joint reinforcement, ft | 1,320 |
House shape compared
Five houses of 3000 sq ft, all with 8 ft walls. Every one of them has the same floor, the same roof area and the same number of rooms available, and the block order moves by six hundred and seventy one.
| House shape | Block to buy | Net wall area | Mortar mix, 80 lb bags |
|---|---|---|---|
| 54.8 by 54.8 ft | 2,070 block | 1,752 sq ft | 152 |
| 50 by 60 ft | 2,079 block | 1,760 sq ft | 153 |
| 40 by 75 ft | 2,174 block | 1,840 sq ft | 160 |
| 30 by 100 ft | 2,457 block | 2,080 sq ft | 180 |
| 25 by 120 ft | 2,741 block | 2,320 sq ft | 201 |
What else matters here
Two thousand and seventy nine block, and the honest version of this answer is that the question cannot be asked in square feet. The floor area of a house does not determine its block count. The perimeter does, and two houses of 3000 sq ft can have very different perimeters.
The table below is five of them, all 3000 sq ft, all with 8 ft walls. A near square at 54.8 by 54.8 is 2,070 block. A long narrow 25 by 120 is 2,741. That is 671 block of difference, about a third again as much wall, on houses with identical floor area, and it comes with proportionally more footing, more mortar, more rebar and more of everything else the wall carries. A square is the least perimeter that encloses a given area, so every step away from square is paid for in exterior wall, which is one of the more expensive things in a house.
Two more things this figure is not. It is a single story with 8 ft walls, so a two story house of the same floor area has a smaller footprint and taller walls and needs its own run. And it deducts no openings: putting 400 sq ft of windows and doors into the same 220 ft of wall takes it from 2,079 block down to 1,607. Measure the actual perimeter off the plan, count the actual openings, and run those, because nothing derived from the square footage alone is going to be close enough to order from.
What this calculator assumes
- Every block here is 8 by 16 nominal on the face, which is the standard unit whatever its width. That works out to 1.125 blocks per square foot of wall, and the figure already contains the 3/8 mortar joint.
- Mortar is the bed and head joints across the face shells, multiplied by 3.6. The multiplier lands the bag count on the coverage printed on the bag, where an 80 pound bag of mortar mix yields about 0.6 cubic feet and lays roughly 13 standard block.
- Grout volume uses the cell section for the block width: about 27 square inches for an 8 inch block, less for a 4 or 6 and more for a 10 or 12. Fully grouting an 8 inch wall works out near 0.28 cubic feet per square foot of wall, which is the figure the block industry publishes.
- Vertical bars are one per grouted cell. On a fully grouted wall they are figured at 48 inches on center instead, because grouting every cell does not mean putting a bar in every cell.
- Horizontal joint reinforcement is every other course, which is 16 inches.
Questions people ask
How many concrete blocks to build a 3000 sq ft house?
2,079 for a 220 ft perimeter with 8 ft walls and no openings deducted. The square footage alone cannot answer it, because the block follows the perimeter.
Why does the shape of the house change the block count?
Because a square encloses a given area with the least perimeter. The same 3000 sq ft is 2,070 block as a near square and 2,741 as a 25 by 120, a difference of 671.
How much do windows and doors reduce the count?
A lot. Deducting 400 sq ft of openings from this wall takes it from 2,079 block to 1,607, so count the real openings off the plan rather than ignoring them.
The concrete block calculator takes any dimensions you like and hands back the same list.