Free UK construction calculators Metric and imperial 2026 UK prices
Work out how much cement and plastering sand you need to render a wall, a gable end or a whole house. Choose the wall behind the render and the coats, enter the size, press Calculate, and see the bags of cement, tonnes of sand, beads and cost.
Cement Needed
0bags
Check the measurements above. The result updates once they look right.
| Coat | Thick | Mix | Cement | Sand |
|---|
Each coat includes your extra for drops and uneven walls.
| Item | Cost |
|---|
Typical 2026 UK prices including VAT. Scaffolding and paint are extra.
The result shows the bags of cement, the tonnes and bulk bags of plastering sand, the water, the beads and the cost, with a coat-by-coat table and a drawing of the wall and a section through the render.
| Coat | Thickness | What it does |
|---|---|---|
| Scratch coat | 8–12 mm | Bonds to the wall and is scratched to key the next coat |
| Float coat (three-coat work) | 8–12 mm | Builds out uneven or very exposed walls |
| Top coat | 6–10 mm | The finish: floated smooth, textured or dashed |
| Two-coat total | 16–20 mm | Most houses and garden walls |
| Three-coat total | 25–30 mm | Exposed coasts and hillsides, uneven old walls |
Keep each coat under about 12 mm. A thick single coat sags, shrinks as it dries and cracks. If a wall needs more than 20–25 mm to get it straight, add a coat, or dub out the hollows first and let them set.
| Wall | Scratch coat | Top coat |
|---|---|---|
| Brick | 1:4 cement:sand | 1:5 |
| Dense concrete block | 1:4 (1:3 on very smooth blocks) | 1:5 |
| Lightweight or aircrete block | 1:5 | 1:6 |
| Old or soft brick | 1:5 or 1:6, or lime render | 1:6 |
The golden rule is that each coat must be the same strength as, or weaker than, the one beneath it, and the render should be weaker than the wall. A strong cement render on a soft wall cannot move with it, so it cracks and lets water in behind. Plasterers often add hydrated lime, for example 1:1:6 cement:lime:sand, or a plasticiser to make the mix easier to work. For old solid-walled houses, a breathable lime render is usually the better choice; see our cement calculator for other mortar jobs.
| Render | Cement per m² | Sand per m² |
|---|---|---|
| Two coats, 12 mm at 1:4 + 8 mm at 1:5, no extra | 7.2 kg | 35 kg |
| Two coats, as above, plus 15% extra | 8.2 kg | 40 kg |
| Three coats, 12 + 10 mm at 1:4 + 8 mm at 1:5, no extra | 11 kg | 52 kg |
So one 25 kg bag of cement does about 3 m² of two-coat render, and a tonne of plastering sand does about 25 m². These figures assume a flat wall. Old brick with hollows and bulges can easily take 25–50% more, which is why the calculator lets you set the extra.
| Area | Cement | Plastering sand | Bulk bags of sand |
|---|---|---|---|
| 10 m² (a garden wall, one side) | 82 kg · 4 bags | 0.40 t | 1 |
| 20 m² (a small extension wall) | 164 kg · 7 bags | 0.80 t | 1 |
| 50 m² (a bungalow front and side) | 411 kg · 17 bags | 1.99 t | 3 |
| 80 m² (a typical semi, outside walls) | 658 kg · 27 bags | 3.18 t | 4 |
| 120 m² (a detached house) | 987 kg · 40 bags | 4.78 t | 6 |
These use two coats, 12 mm at 1:4 and 8 mm at 1:5, with 15% extra, after taking off doors and windows. Work out the pointed top of a gable end separately with the Gable End shape, and add it to the rest.
Use plastering sand, also sold as rendering sand: a washed, well-graded sharp sand. Soft building sand has fine clay particles that make render shrink and crack. NHBC guidance asks for coarser sand in the undercoats for strength and finer sand in the finishing coat. Keep the same sand from the same supplier for the whole job, because different sands dry to different colours. Our sand calculator covers other uses.
Sand weights vary with moisture. We use 1.6 tonnes per m³ of loose plastering sand and 850 kg bulk bags, the same figures as our mortar and screed calculators.
Beads give render straight, strong edges. The calculator counts a bellcast bead along the bottom of the wall, which throws rainwater off the render above the damp-proof course, and an angle bead up each outside corner. Beads usually come in 2.5 m and 3 m lengths, in stainless steel or PVC. You may also want stop beads round windows and doors, and expansion beads on long walls or where two materials meet, so add those to your order separately.
| Item | Typical 2026 UK price |
|---|---|
| Cement, 25 kg bag | £7–£8 |
| Plastering sand, bulk bag | £55–£75 |
| Render bead, 2.5 m | £3–£6 |
| Sand and cement render, fully applied | £40–£60 per m² |
| Monocouche (through-coloured) render | £55–£80 per m² |
| Masonry paint, two coats, applied | £8–£15 per m² |
| Scaffolding for a semi-detached house | £800–£1,200 |
Sand and cement is the cheapest render, but labour is most of the price: the materials are only around £5–£8 per m². Painted sand and cement render needs repainting every 5–8 years, while monocouche and silicone renders are coloured all the way through. Scaffolding is often the biggest single extra, so price it with our scaffolding cost calculator and get at least three written quotes.
Re-rendering a house can count as renovating a thermal element. In England, if you render more than 50% of an individual outside wall, or more than 25% of the whole outside of the building, you normally need Building Regulations approval and should add insulation where it is practical, as set out in Approved Document L. That is often the moment to consider external wall insulation instead of plain render.
Rendering is usually permitted development if the finish is similar to the rest of the house. You need planning permission in a conservation area, on a listed building, or where your permitted development rights have been removed. Ask your council if you are not sure.
Area = wall area − doors and windows · Gable = width × eaves height + width × (ridge − eaves) ÷ 2
Each coat: render (m³) = area × thickness × (1 + extra %) · Dry materials = render × 1.33
Cement (kg) = dry ÷ (1 + sand parts) × 1,440 · Sand (t) = dry × sand parts ÷ (1 + sand parts) × 1.6
The 1.33 allows for the sand and cement shrinking when water is added, and the cement is added up across the coats before rounding up to whole 25 kg bags. Below half a tonne, the sand is shown in 25 kg bags. Beads are the length along the bottom of the wall plus one corner bead up the height of each outside corner, in 2.5 m lengths. The cost is the bags, sand and beads at your prices, plus labour per m².
About 7–8 kg for two-coat render, 20 mm thick, at 1:4 and 1:5. One 25 kg bag of cement covers about 3 m².
About 35–40 kg of plastering sand per m² for two coats, 20 mm thick, so a tonne of sand does about 25 m².
1:4 cement to plastering sand for the scratch coat and 1:5 for the top coat on brick or dense block. Use 1:5 and 1:6 on lightweight blocks or soft brick.
16–20 mm in total for two coats: a scratch coat of 8–12 mm and a top coat of 6–10 mm. Keep each coat under about 12 mm.
No. Use plastering or rendering sand, which is washed and sharper. Soft building sand makes render shrink and crack.
Usually two to five days, depending on the weather. The scratch coat should be firm but still slightly damp when the top coat goes on.
Sand and cement render costs about £40–£60 per m² applied, plus scaffolding. A typical semi with 80 m² of outside wall costs about £3,200–£4,800 before scaffolding and paint.
Usually not for planning, unless you are in a conservation area or the house is listed. Re-rendering most of a wall may need Building Regulations approval and extra insulation.
Coat thicknesses and mixes follow common UK practice for sand and cement render. Cement at 1,440 kg/m³, plastering sand at 1.6 t/m³ and a dry volume factor of 1.33, as across ConstructionMath. Default prices are typical 2026 UK merchant prices including VAT, and applied costs come from 2026 UK cost guides; prices vary by region and supplier. Reviewed November 2026.