How many bricks and blocks per square metre?
A standard UK brick (215 x 102.5 x 65 mm) with 10 mm joints takes about 60 bricks per m2 in a half-brick wall and about 120 in a one-brick wall. A standard 440 x 215 mm block takes about 10 per m2. Add an allowance for waste and take off the openings.
The short answer
These are the usual figures for a UK standard brick and a standard block, laid with 10 mm mortar joints:
- half-brick wall (one skin, 102.5 mm thick): about 60 bricks per m2
- one-brick wall (two skins, 215 mm thick): about 120 bricks per m2
- blocks, 440 x 215 mm on the face: about 10 per m2, whatever the thickness of the block
A cavity wall with a brick outer leaf and a block inner leaf therefore needs about 60 bricks and 10 blocks for every m2 of wall.
The sum, so you can check it
Each brick takes up its own size plus one joint on the length and one on the height:
- length plus joint: 215 + 10 = 225 mm
- height plus joint: 65 + 10 = 75 mm
- area per brick on the face: 225 x 75 = 16,875 mm2
- bricks per m2: 1,000,000 / 16,875 = 59.3, so call it 60
A quick cross-check: 1,000 / 225 is about 4.4 bricks along a metre, and 1,000 / 75 is about 13.3 courses up a metre. 4.4 x 13.3 is about 59 again. A one-brick wall is two skins, so double it to about 120.
For blocks: (440 + 10) x (215 + 10) = 450 x 225 = 101,250 mm2, and 1,000,000 / 101,250 = 9.9, so about 10 per m2.
If your bricks are a different size, or you are laying to a joint other than 10 mm, put your own sizes into the same sum.
Take off the openings
Work out the gross area of the wall (length x height), then deduct each door, window and other opening (width x height). Count the net area only. Bricks cut around lintels, reveals and corners are covered by the waste allowance, not by shrinking the deduction.
Allow for waste
A common rule of thumb is to add 5 to 10 percent for breakage, cuts and mistakes. It is a judgement call. Use the lower end for a plain straight wall with a careful gang and good storage. Use the higher end for lots of corners, piers, arches, cut bricks, patterns, reclaimed or soft bricks, or deliveries that will be moved about site.
Buy all the bricks for a face from the same batch where you can, because colours vary between batches. That is a reason to order a little over rather than top up later.
Worked example: a garden wall
A half-brick garden wall 8 m long and 1.8 m high, with a gateway opening 1 m wide and 1.8 m high:
- gross area: 8 x 1.8 = 14.4 m2
- less the opening: 1 x 1.8 = 1.8 m2, leaving 12.6 m2
- bricks: 12.6 x 60 = 756
- with 5 percent waste: 756 x 1.05 = about 794. With 10 percent: 756 x 1.10 = about 832
So order somewhere between 800 and 850, rounded up to whole packs. Piers, coping and a damp-proof course are extra and need their own take-off.
A 10 m long, 2.4 m high block wall with one 0.9 x 2.1 m door: 24 - 1.89 = 22.11 m2, times 10 = 222 blocks, and about 233 with 5 percent for cuts.
Mortar (approximate only)
Mortar is harder to pin down, because it depends on the joint, how full the bricks are and how much is dropped or left in the bucket. As a rough guide, the joints in a half-brick wall come to something like 0.02 m3 (20 litres) of mortar per m2 of wall before waste. Treat that as an approximate figure, allow extra, and check the quantity with your supplier or the mix manufacturer.