Sharp sand vs building sand: which do you need?

The short answer

Use building (soft) sand for bricklaying mortar and pointing, and sharp sand for screeds, concrete and bedding paving. Plastering sand sits in between and is made for render.

Why they behave differently

Sand is graded by the size and shape of its grains. Building sand has fine, rounded grains, so mortar made with it is smooth, sticky and easy to spread off a trowel. That workability is what a bricklayer wants, but it also makes the sand weak on its own.

Sharp sand has coarser, angular grains that lock together. It drains well and gives strength, which is why it is used where a mix has to carry load or stay firm underfoot, but it makes a harsh, gritty mortar.

Which sand for which job

• Bricklaying and blockwork mortar: building sand, with cement and plasticiser or lime.
• Pointing and repointing: building sand, matched in colour to the existing joints.
• Floor screeds: sharp sand with cement, laid fairly dry.
• Concrete: sharp sand with gravel, or all-in ballast which already combines them.
• Bedding block paving and patio slabs: sharp sand.
• Filling block paving joints: kiln dried sand, which is fine and completely dry so it brushes in.
• Render: plastering sand, which is graded to spread evenly and resist cracking.

Bags or bulk bags?

Small bags suit repairs and short runs of wall. For a full floor screed, a patio or a large amount of bricklaying, a bulk bag is usually far better value and saves repeated trips. Store sand covered so it stays dry and clean.