Guide
Building sand vs sharp sand: which do you need?
Use soft building sand for bricklaying and blocklaying mortar because its fine, rounded grains make a smooth, sticky mix; use sharp sand for concrete, floor screeds and paving beds where strength and drainage matter.
Written by the SK Trade team. Last reviewed 1 November 2026.
The difference in one line
Building sand (soft sand) has fine, rounded grains and a little clay content, which makes mortar workable. Sharp sand (grit sand) has larger, angular grains that lock together, which makes it stronger and free-draining.
What each one is for
| Job | Sand |
|---|---|
| Bricklaying and blocklaying mortar | Soft building sand |
| Floor screeds | Sharp sand |
| Site-mixed concrete | Sharp sand with gravel, or all-in ballast |
| Bedding paving slabs | Sharp sand |
| Render and sand-and-cement plaster | Plastering sand |
| Filling block-paving joints | Kiln-dried sand |
How much sand?
Sand is sold by weight. As a rough guide, one cubic metre of sand weighs 1.5 to 1.7 tonnes depending on how damp it is. For mortar, 1,000 bricks need about 1 tonne of building sand. For a 50 mm screed, each square metre needs about 0.05 m³, or roughly 80 kg of sharp sand.
Bulk bags or small bags?
Bulk bags typically hold around 850 kg, though weights vary by supplier. For anything more than a few small bags, a bulk bag is usually better value and easier to manage. Cover bags so the sand does not dry out, get saturated or collect debris.
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Related questions
How much does a bulk bag of sand weigh?
Around 850 kg is typical, but bag weights vary between suppliers. We confirm the weight with your price.
How many bags of cement for 1,000 bricks?
At a 1:4 mortar mix, about 8 to 9 bags of 25 kg cement and roughly 1 tonne of building sand, allowing for waste.
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