Bricks, screed, render and fencing: four takeoffs to get right

Bricks, screed, render and fencing may belong to one project, but they use different physical quantities. Bricks start from wall area, screed from volume, render from area and consumption, and fencing from length and intervals.

1. Bricks: start from net wall area

An 8 m × 2.5 m wall is 20 m². A 1.20 m × 2.10 m opening is 2.52 m², leaving 17.48 m².

At an assumed 50 bricks/m²:

17.48 × 50 = 874 bricks

With 5% allowance, that becomes 917.7, so at least 918 units before packaging. The brick calculator automates the sequence. For concrete blocks, use the dedicated block calculator.

2. Screed: area becomes volume

For a 7 m × 4 m room, area is 28 m². At 5 cm = 0.05 m thickness:

28 × 0.05 = 1.40 m³

The screed calculator makes the unit conversion explicit. Average thickness matters: over 60 m², increasing from 5 to 5.5 cm changes volume from 3.00 to 3.30 m³.

3. Render: area × thickness × consumption

Single-coat render data sheets give consumption per millimetre of thickness, often around 1.3 to 1.8 kg/m²/mm, so the thickness comes first. NF DTU 26.1 requires at least 10 mm at every point for single-coat render; an average of 15 mm keeps a reasonable margin.

At 15 mm and an assumed 1.5 kg/m²/mm:

15 × 1.5 = 22.5 kg/m²

For 40 m²:

40 × 22.5 = 900 kg

With 10% allowance: 990 kg. In 25 kg bags, 990 ÷ 25 = 39.6, so 40 bags are required.

Use the render calculator, but enter the thickness and the consumption of the actual product: consumption depends on the product, and an uneven substrate forces local build-ups that increase the real need.

4. Fence: count intervals before posts

For a 20 m straight fence with a maximum 2.5 m spacing:

20 ÷ 2.5 = 8 intervals

A simple open line with eight intervals generally has nine post positions before accounting for gates, corners or special posts. If the length is 21 m, 21 ÷ 2.5 = 8.4, so eight intervals would exceed the chosen spacing and nine are needed.

The fence calculator helps explore this rounding effect.

Four methods side by side

Work	Starting measure	Intermediate rule	Purchasing result
Bricks	wall m²	bricks/m²	units/pallets
Screed	m² + thickness	m³	volume/material
Render	m² + thickness	kg/m² (mm × kg/m²/mm)	kg/bags
Fence	length	intervals	posts/panels

Do not use the same allowance everywhere

Brick losses, render consumption uncertainty, screed thickness variation and fence geometry are different risks. When uncertainty comes from a measurement, comparing a low and high scenario can be more informative than adding an arbitrary percentage.

For 50 m² of screed, 5 cm gives 2.50 m³ while 6 cm gives 3.00 m³: a 0.50 m³ difference.

Keep the assumptions with each result-dimensions, openings, thickness or consumption, allowance and packaging-so the calculation remains understandable if the product or measurement changes.

For a reusable method across the whole project, see planning the right material quantities.