What is the mix ratio for sand and cement render?

The standard mix for external rendering in the UK is 1:5 (1 part cement to 5 parts sharp sand) for a general-purpose render. A stronger 1:4 mix is used for the scratch coat or in exposed locations. Always use sharp sand (not building sand) and add plasticiser to improve workability.

How many coats of render do I need?

Traditional sand and cement rendering typically requires 2 coats — a scratch coat (8-10mm) and a top coat (6-8mm), giving a total thickness of around 15-20mm. Monocouche (one-coat) render is applied in a single 20-25mm coat. Silicone and acrylic renders are usually applied in 1-2 thin coats (1.5-2mm each) over a base coat system.

How much sand do I need per m²?

For sand and cement render at 15mm thickness per coat, you need approximately 0.2 tonnes (200kg) of sharp sand per m² for one coat. So 1 tonne of sand covers roughly 5 m² per coat. For a typical 2-coat system, 1 tonne covers about 2.5 m² of wall.

What is monocouche render?

Monocouche (meaning 'one coat' in French) is a factory-made render that combines cement, aggregates, and additives. It is applied in a single 20-25mm coat, saving time compared to traditional 2-coat rendering. Popular UK brands include Weber, K Rend, and Parex. It comes pre-coloured, so no painting is needed.

How long does render take to dry?

Sand and cement render should be kept damp for the first 2-3 days to prevent cracking, then allowed to dry for at least 7 days before the next coat. Monocouche render typically needs 24-48 hours before it can be finished. Full curing takes 28 days for cement-based renders. Do not render in freezing conditions. For internal plaster drying, see our Plaster Drying Time Estimator.

Rendering Calculator — How Much Sand and Cement for Rendering?

Rendering Calculator — Sand, Cement & Render Materials

Calculate how much sand, cement, or render you need per square metre for external walls. Covers sand and cement, monocouche, silicone, and acrylic renders.

Wall Height

Wall Length

Number of Walls

Render Type

Number of Coats

2 coats is standard for sand & cement

Mix Ratio

1:5 is standard; 1:4 for scratch coat

Include wastage allowance

Adds 10% extra for mixing and application losses

Wastage Percentage

10% is standard for rendering

Price Per Cement Bag (optional)

Price per 25kg bag of cement

Price Per Tonne of Sand (optional)

Price per tonne of sharp sand

How We Calculate This

Our rendering calculator works by computing the total wall area and then calculating material quantities based on your chosen render type and number of coats. For sand and cement, we calculate both cement bags and sharp sand tonnage separately.

The formula

Sand & cement: Total area × Coats ÷ 5 = Tonnes of sand. Cement bags calculated from the mix ratio (3.5 bags per tonne at 1:5, or 4.5 bags per tonne at 1:4).

Monocouche: Total area × Coats ÷ 1.5 = Number of 25kg bags needed.

Silicone/Acrylic: Total area × Coats ÷ 3.5 = Number of 25kg buckets needed.

Coverage rates

Sand & cement: 1 tonne of sharp sand covers ~5 m² per coat at 15mm
Monocouche: 1 × 25kg bag covers ~1.5 m² at 20mm thickness
Silicone render: 1 × 25kg bucket covers ~3.5 m² at 1.5mm thickness
Acrylic render: 1 × 25kg bucket covers ~3.5 m² at 1.5mm thickness

These rates are based on typical UK application thicknesses. Actual coverage varies depending on surface texture — rough blockwork will absorb more material than smooth concrete. The 10% wastage factor accounts for normal losses during application.

Frequently Asked Questions

Last updated: February 2026

All calculations are estimates. Verify with your supplier.

Rendering Calculator — Sand, Cement & Render Materials

How We Calculate This

The formula

Coverage rates

Frequently Asked Questions

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