Five hundred concrete blocks take about 17 bags of masonry cement and 2.1 tons of sand. The same blocks laid with bagged mortar mix take 32 bags of 80 lb, and with site-mixed Type S mortar 11 bags of portland cement, 5 bags of lime and 2 tons of sand. The calculator above works this out from the number of blocks or brick you are laying, or from a volume of mortar, for any of the four ASTM C270 mortar types.
How the calculator works
Start from what you know. If you know how many blocks or brick you are laying, enter the count: the calculator uses the masons' batch figures, which already include waste. If you know the volume, from a joint calculation or a specification, enter it with a waste allowance. Then pick the mortar type and how you will buy it.
From blocks or brick
NCMA TEK 04-02A Table 2 lists how many units one batch of mortar lays, for conventional 8 × 16 in block with face-shell bedding and for brick-sized units with full bedding:
| One batch | 8 × 16 block | Brick |
|---|---|---|
| 8 bags (70 lb) masonry cement + 1 ton sand | 240 | 1,000 |
| Type S: 1 bag portland, ½ ft³ lime, 4½ ft³ sand | 46 | 225 |
| One 80 lb bag of mortar mix | 16 | 50 |
The figures vary with the mason, the layout and the weather; manufacturers quote slightly different yields for their mixes, for example up to 13 blocks or 37 brick per 80 lb bag. They are good for ordering, not for a joint-by-joint calculation.
From a volume
Masonry sand bulks when damp, and the cementitious materials fill the spaces between the grains, so one cubic foot of damp loose sand makes about one cubic foot of mortar (BIA Technical Note 10). The sand you need is therefore the mortar volume, and the cement and lime follow from the mix ratio. One ton of damp sand is about 25 ft³.
Mortar types and mix ratios
ASTM C270 defines four types by their proportions or by their tested properties. Under the proportion specification, sand is between 2¼ and 3 times the total volume of cement and lime; the batches below use 3, as NCMA's table does.
| Type | Portland : lime : sand | Masonry cement : sand | Typical use |
|---|---|---|---|
| M | 1 : ¼ : 3¾ | 1 Type M : 3 | Foundations below grade, retaining walls |
| S | 1 : ½ : 4½ | 1 Type S : 3 | Reinforced masonry, below grade, high wind or seismic areas |
| N | 1 : 1 : 6 | 1 Type N : 3 | General work above grade, brick veneer |
| O | 1 : 2 : 9 | 1 Type N : 3 | Interior non-load-bearing walls, repointing soft brick |
For batching, a 94 lb bag of portland cement counts as 1 ft³ and a 50 lb bag of hydrated lime as 1¼ ft³. A 70 lb bag of masonry cement is about 1 ft³; check the bag, since manufacturers print the weight per cubic foot. On site, sand is measured with a shovel: about seven shovelfuls make a cubic foot, so a Type S batch for one bag of cement takes around 31 shovelfuls of sand.
Which mortar to buy
- Masonry cement and sand is the usual choice for block and brick jobs of any size: one bag type, sand by the ton.
- Portland cement, lime and sand lets you hit an exact proportion and is common where the specification calls for cement-lime mortar.
- Mortar mix in 80 lb bags needs only water, about 5 quarts per bag, and suits small jobs and repairs. For hundreds of blocks it gets heavy and expensive: 500 blocks take 32 bags.
Common mistakes
- Using a stronger mortar than needed. Type M is not better for brick veneer: a mortar stiffer than the brick cracks the brick instead of the joint. Type N is the usual veneer mortar.
- Adding sand to the mortar volume. Sand and mortar volumes are about equal; you do not add the cement on top of the sand.
- Ordering by joint volume. The joints of 1,000 modular brick hold about 8 ft³ of mortar, but a job uses about three times that.
To count the units first, use the Concrete Block Calculator or the Brick Calculator.