Sub-base and aggregates
Sand blinding tonnes
- where
- volume (m³)
- area (m²)
- blinding thickness (mm)
- material to order (t)
- density as laid (t/m³)
- margin (%)
Explain this equation
This gives the tonnes of sand needed to blind a sub-base or bed paving over a given area and thickness.
A is the area, t the blinding thickness in millimetres and V the volume. ρ is the density of the sand as laid and w is a small margin for waste and levels.
Volume is area times thickness, with /1000 converting millimetres to metres. Weight is volume times density, increased by the margin.
Sense check: 25 mm over 40 m² is 1 m³, about 1.9 t of damp sand, or 2 t with a 5% margin.
Watch out: damp sand is heavier per m³ than dry sand; use your supplier’s figure if they give one.
Tonnes of sand to blind a sub-base before a damp-proof membrane or slab, or to bed paving.
Enter your values to see the result.
Good to know
Caterpillar gives damp sand as 1.90 t/m³ in place and 1.69 t/m³ loose; dry sand 1.60 and 1.42. Aggregate suppliers suggest allowing about 5% extra. Blinding over Type 1 is usually just enough to fill the surface voids and protect the membrane from puncture; follow the slab design or membrane manufacturer for thickness.
Common mistake
Blinding too thick. A deep sand layer can settle and is not a substitute for compacted sub-base.
Limits
Density depends on moisture and grading. Use the supplier’s figure if known.
Sources
Results are calculations from the published methods and figures shown, and depend on the data you enter. Follow BS 8500, BS EN 206, BS EN 752, Building Regulations Part H, manufacturers’ data and your engineer’s design. Structural concrete and foundations need a competent designer.