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Brick calculator: bricks, blocks and mortar for a wall
Work out how many bricks a wall needs, plus the blocks, cement, lime and building sand to lay them. UK standard bricks with 10mm joints are 60 per square metre in a half-brick wall and 120 in a one-brick wall, and the mortar is worked out by designation (M4 for general facing brickwork) so it is weaker than the brick, as it should be.
What you need
Bricks and blocks
- Wall area
- 6.0 m²
- Bricks
- 378 bricks60 per m² in a half-brick wall, plus wastageImperial Bricks per-m² guide
- Packs to order
- 1 × packs of 500you cannot buy a part pack
Mortar
- Mortar (muck)
- 378 kg wet1kg a brickTarmac Blue Circle QA mortar yields
- Cement (OPC), M4 at 1:6 with plasticiser
- 3 × 25kg bagsparts are by volume, so this is a working figureMarshalls BTB4; MPA Mortar Data Sheet 19
- Plasticiser (feb)
- 0.2 litres60 to 90ml per bag of cement
- Building sand (soft sand)
- 13 × 25 kg bags324kg. Bulk bags are about 800kg, not a tonneSelco; BMF bulk bag minimum 800kg
Round up to whole packs and bags. Figures include the wastage you chose and match TradeCalc in the app.
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Or claim your free profile link nowHow the maths works
- UK standard bricks are 215 × 102.5 × 65mm. With a 10mm joint that is 60 per square metre in a half-brick wall and 120 in a one-brick wall (Imperial Bricks). Hybrid 73mm and imperial 68mm bricks are 54, imperial 73mm is 51 and imperial 75mm is 50. For anything else, put in the size and joint and it works out 1,000,000 ÷ ((length + joint) × (height + joint)).
- Doors deduct 1.9m² and windows 1.4m² each by default; change the sizes if yours are different. Blocks for a cavity inner leaf are 10 per square metre of the same net area (Jewson), not worked back from the bricks.
- Mortar is 1kg wet per brick in a half-brick wall. A one-brick wall has a collar joint between the two skins, so it is 1.3kg a brick (Tarmac Blue Circle QA mortar: 1,800 to 2,000 bricks per m³ half-brick, 1,400 to 1,600 in a 215mm wall). Blocks take 0.012m³ per m² of 100mm blockwork and 0.016m³ per m² of 140mm at 1,800kg per m³.
- The mix is a designation, not a strength guess. M4 (iii), 1:1:6 or 1:5 to 6 with plasticiser, is the general-purpose mix for facing brickwork above and below DPC. M6 (ii) is for copings, cills and sheltered engineering brick below DPC; M12 (i) only for engineering brick in retaining walls and manholes; M2 (iv) internal only (Marshalls BTB4 bulletin; MPA Mortar Data Sheet 19). The mortar must be weaker than the brick so movement cracks the joint, not the brick.
- Cement, lime and sand are split by parts, with cement and lime in 25kg bags. Plasticiser replaces the lime at 60 to 90ml per bag of cement. Sand is shown in bulk bags of about 800kg (Selco 750 to 850kg; the BMF minimum is 800kg) or 25kg bags for small jobs.
- A brick-on-edge coping runs on the 75mm module, 13.3 bricks a metre. Two courses of engineering bricks below DPC are worked out on the 225mm stretcher module for each skin, with a 30m roll of 100mm DPC for a half-brick wall or 225mm for one-brick.
- Wastage covers cuts and breakages: 5% for a straight wall, 7% for piers, curves and detailing. Packs are 400 to 500 bricks, so the pack count rounds up.
Worked example
A 6m long, 1m high half-brick garden wall is 6m². At 60 bricks per m² with 5% waste that is 378 bricks, one pack of 500, and about 378kg of M4 mortar: 3 bags of cement, 13 bags of building sand and a splash of plasticiser at 1:6. Mixed with lime at 1:1:6 instead it is 2 bags of cement, 2 of lime and 12 of sand.
Questions people ask
How many bricks are in a square metre?
60 for a half-brick (single skin) wall with standard 215 × 102.5 × 65mm bricks and 10mm joints, 120 for a one-brick wall. Bigger bricks need fewer: 54 for hybrid 73mm or imperial 68mm, 51 for imperial 73mm, 50 for imperial 75mm. A pack is 400 to 500, so 1,000 bricks is two or three packs.
How much mortar do I need per brick?
About 1kg of wet mortar (muck) per brick in a half-brick wall, so 1,000 bricks needs about a tonne of mortar. In a one-brick wall the collar joint takes it to 1.3kg. At M4 with plasticiser that tonne is about 6 bags of cement and a bulk bag of building sand; with lime it is 5 bags of cement, 5 of lime and 750kg of sand.
What mortar mix for a garden wall?
M4, designation (iii): 1:1:6 cement:lime:sand, or 1:5 to 6 cement:sand with plasticiser. That is the general-purpose mix for facing bricks above and below DPC. Go up to M6 (1:½:4½ or 1:3 to 4) for copings and cills, and only use M12 (1:3) with engineering bricks in retaining walls or manholes. A 3:1 mix under ordinary facing bricks is too strong: the joint should always be weaker than the brick.
Bulk bag or 25kg bags of sand?
A bulk (jumbo) bag is about 800kg, not a tonne: Selco quote 750 to 850kg and the BMF minimum is 800kg. The calculator switches to bulk bags above 400kg of sand. For a small repair, 25kg bags from the merchant are easier to handle.
Should I add wastage?
Yes. Bricks break, cuts are wasted and a pack rarely arrives perfect. 5% is normal for a straight wall, 7% for piers, curves and brick-on-edge detailing, and you round up to whole packs anyway.
Does this include the foundation?
No. Use the concrete calculator for the footing. A garden wall over about 1m usually needs a 600mm wide strip footing, and two courses of engineering bricks with a DPC keep the facing bricks out of the wet ground.
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