How Much Mortar per m² of Brickwork and Blockwork?

A single-leaf brick wall built from 215 by 102.5 by 65 mm bricks with 10 mm joints holds about 0.018 m³ of mortar per m² (18 litres) of wall face. Blockwork in 440 by 215 by 100 mm blocks with the same joints holds about 0.0066 m³ per m² (6.6 litres). In imperial, that is roughly 0.058 cu ft per sq ft for brick and 0.021 cu ft per sq ft for 100 mm block.

Assumptions: single leaf, one bed joint and one head joint per unit, joints filled solid, no collar joint, and no waste added. Those are the figures for the mortar that ends up in the wall, not the material you buy.

Everything past this point is about the four things that move those numbers: unit size, joint thickness, wall build-up, and how much you lose on site.

Brickwork per m² and per sq ft

Brick sizes vary by country, and the mortar figure moves with them, so pick the row that matches the brick you are actually laying.

Assumptions: single leaf or single wythe, running bond, one bed joint and one head joint per brick, joints filled solid through the full brick width, no collar joint, no waste. Mortar volumes are wet mortar in place.

The Indian 190 by 90 by 90 mm brick is the outlier because it is much thinner front to back (90 mm against 102.5 mm), and mortar volume scales directly with wall thickness.

Note that the US and UK figures land within 6 percent of each other despite different brick shapes. That is not a coincidence. Mortar volume per square metre depends mostly on joint thickness as a fraction of the coursing, and both traditions settled on roughly the same fraction.

Blockwork per m² and per sq ft

Block units are larger, so the joint count per square metre drops sharply. Block width, on the other hand, raises the mortar per unit in direct proportion.

Assumptions: single leaf, running bond, full mortar bedding across the whole block width, 10 mm or 3/8 in bed and head joints, no waste. US figures use the actual dimensions of nominal 4, 6, 8 and 12 in units, which are 3/8 in smaller than nominal in each direction.

Two qualifications matter here.

Full bedding versus face-shell bedding. Hollow concrete blocks are usually laid with mortar on the two outer face shells only, not across the cross webs. That uses roughly a third of the full-bed figure. The Concrete Masonry and Hardscapes Association bases its estimating guidance on face-shell bedding, and notes mortar quantity is the item most often misestimated on a block job.

Block width does not change the block count. You get about 9.9 blocks per m² whether the block is 100 mm or 215 mm wide, but the mortar per m² doubles across that range. Confirm the block width before you order.

The effect of joint thickness

Joint thickness enters the calculation twice, through the bed joint and the head joint, so it has a bigger effect than most people expect.

Assumptions: single leaf, full bed, no waste. Imperial joints are 1/4, 3/8 and 1/2 in; the metric column headings pair them with their nearest metric equivalents rather than converting exactly.

Moving a brick wall from a 1/4 in joint to a 1/2 in joint raises the mortar by about 80 percent. That is why the mortar joint thickness guide is worth reading before you fix an estimate, and why the calculator asks for the joint rather than assuming one.

Wall thickness and what the per-m² figure covers

The figures above are for one leaf or one wythe, with the mortar going through the full thickness of the unit. Three build-ups change that.

A cavity wall or a two-leaf wall is two separate walls. Add the two rows together. A brick outer leaf at 0.0176 m³/m² with a 100 mm block inner leaf at 0.0066 m³/m² comes to 0.0242 m³/m² before waste.

A solid two-wythe wall with a filled collar joint adds the vertical joint between the wythes. The Brick Industry Association puts that at 3.13 cu ft per 100 sq ft for a 3/8 in collar joint, which is 0.0095 m³/m², and it is easy to forget because it does not show on the face of the wall.

Headers and bonds other than running bond raise both the brick count and the mortar. BIA Technical Note 10 gives correction factors, for example a common bond with full headers every fifth course adds one fifteenth to the mortar quantity.

From wall area to material: a worked 10 m² example

Take 10 m² of single-leaf brickwork in 215 by 102.5 by 65 mm brick, 10 mm joints, mixed on site as a Type N mortar at 1 part cement, 1 part lime and 6 parts sand.

Bricks       = area × bricks per m²
Wet mortar   = area × mortar per m²
Dry material = wet mortar × 1.33
Order volume = dry material × (1 + waste)
Each material = order volume × (its parts ÷ total parts)

1. Bricks = 10 m² × 59.3 = 593 bricks, or 623 with 5 percent for breakage
2. Wet mortar = 10 m² × 0.0176 m³ = 0.176 m³ (176 litres)
3. Dry material = 0.176 × 1.33 = 0.234 m³
4. Plus 10 percent waste = 0.258 m³
5. Cement = 0.258 × 1/8 = 0.032 m³, about 46 kg, or one 50 kg bag
6. Hydrated lime = 0.258 × 1/8 = 0.032 m³, about 21 kg
7. Sand = 0.258 × 6/8 = 0.193 m³, about 310 kg

Step 3 is the step most guides skip. Dry cement, lime and sand occupy roughly a third more volume than the mortar they produce, because once water is added the cement paste fills the spaces between the sand grains. If you buy 0.176 m³ of dry material you will end up about a quarter short. The full derivation is in the brickwork mortar calculation guide.

The kilogram figures use common loose bulk densities of about 1,440 kg/m³ for cement, 640 kg/m³ for hydrated lime and 1,600 kg/m³ for sand. Your supplier’s figures may differ, and damp sand bulks up considerably, so treat those as order-sizing numbers rather than exact weights.

Buying bags instead

If you are buying pre-blended bags rather than raw materials, the mortar per m² still tells you the volume, but the bag count follows the manufacturer’s coverage figure rather than the volume. Those figures build in a much larger practical allowance than a 10 percent waste factor, and the bag coverage guide sets the two side by side and explains the gap.

As a quick cross-check for a metric job: one 25 kg bag of pre-blended mortar covers roughly 0.4 m² of single-leaf brickwork or about 0.9 m² of 100 mm blockwork, based on the published brick and block coverage figures scaled by bag weight.

How the calculator handles it

The Mortar Calculator works the same volume method rather than applying a flat per-m² rule. It takes the wall length, height and thickness, subtracts the volume of the units at your chosen size and joint, converts wet mortar to dry material, then applies your waste factor. Switch the unit toggle to metric and it reads metres and centimetres and returns cubic metres.

Because it works from your actual unit and joint dimensions, it will not always match a table row. That is the point. A per-m² figure is a planning number for ordering sand and quoting; the calculation from your own dimensions is the one to buy from.

What the area method misses

Multiplying wall area by a per-m² figure is fast and accurate for the main run of a wall. Four things sit outside it, and on a small job they add up.

Openings. Take the area of doors and windows out of the gross wall area before you multiply. On a house elevation that can be 15 to 25 percent of the face.

Returns, reveals and corners. Corners need cut units and extra handling, and reveals around openings often get a fuller joint than the open run of a wall. The brick count rises more than the mortar does, but both rise.

Bed joints on the starting course. The first course over a foundation is laid on a thicker bed to take up level, and masonry specifications allow that bed to run up to 3/4 in (19 mm). On a long low wall, that one course can add several percent to the total.

Pointing and repointing. If you are raking and repointing rather than laying new work, the area method does not apply at all. Repointing fills a raked joint typically 2 to 2.5 times its width deep, so the volume comes from joint length times joint width times rake depth, not from wall thickness.

For a single small wall, none of this changes the order much. For a house or a boundary wall with several returns, work the elevations separately and add them, rather than taking a single rectangle.

Sense-checking a per-m² figure

Published figures for mortar per m² range widely, and some of that range is real while some of it is sloppy sourcing. Three checks catch most errors.

Does it say whether it includes waste? A brickwork figure of 0.022 to 0.025 m³/m² is a waste-inclusive number. A figure of 0.017 to 0.018 m³/m² is net. Both are defensible; a figure quoted without saying which is not.

Does it name the brick? A 190 mm brick and a 230 mm brick differ by 30 percent in mortar per m². A number with no unit size attached cannot be checked.

Does it say how many leaves? Cavity wall figures are roughly double single-leaf figures, and articles that mix the two are the most common source of large errors in mortar estimates.