Exterior
Exterior masonry paint (smooth or textured surfaces)
- where
- masonry paint needed (L)
- wall area less openings (m²)
- number of coats
- spreading rate for the surface (m²/L)
- waste and touch-up allowance (%)
- tins to buy
- tin size (L)
Explain this equation
Works out masonry paint for an exterior wall and the tins to buy.
Area times coats divided by spreading rate gives litres; the waste allowance is added and the result divided by the tin size, rounded up.
Coverage arithmetic: litres equal area times coats divided by spreading rate.
Sense check: 60 m² in two coats at 16 m²/L with 10% waste is about 8.3 litres, one 10 litre tin.
Watch out: spreading rates fall sharply on rough or textured surfaces such as pebbledash, often to a third or less of the smooth figure.
Works out masonry paint for render, brick or pebbledash. Texture and porosity cut coverage sharply, so pick the spreading rate for the surface.
Enter your values to see the result.
Good to know
Dulux Trade Weathershield Smooth Masonry: up to 16 m²/L on smooth low-porosity render, 4–6 m²/L on pebbledash. Weathershield Textured: 6–8 m²/L on smooth render, 3–4 m²/L on pebbledash. Farrow & Ball Exterior Masonry: 40 m² per 5 L (8 m²/L). Two full coats is normal; seal new or bare surfaces with a first coat thinned up to 1 part water to 5 parts paint (use the mist coat calculator for the split). Check the weather window and surface temperature on the technical page.
Common mistake
Pricing pebbledash at the smooth-render rate. Pebbledash can take three or four times as much paint.
Limits
Average rates; very porous or friable surfaces need a stabilising solution first. Scaffold, access and masking are not included.
Sources
- Dulux Trade Weathershield Smooth Masonry Paint data sheet (up to 16 m²/L on smooth low-porosity render; 4–6 m²/L on pebbledash; thin first coat up to 1:5 on new or bare surfaces; 2.5, 5, 7.5, 10 L)
- Dulux Trade Weathershield Textured Masonry Paint data sheet (6–8 m²/L on smooth render; 3–4 m²/L on pebbledash; normal thinning max. 1 part water to 10 parts paint)
- Farrow & Ball, How much paint do I need? (coverage per tin, e.g. Estate Emulsion 70 m² per 5 L; Masonry & Plaster Stabilising Primer 100 m² per 5 L; one primer & undercoat plus two topcoats)
- BS 6150:2019 Painting of buildings. Code of practice
Results are calculations from the published methods and figures shown, and depend on the data you enter. Coverage depends on the product, surface and application. Always follow the paint and wallcovering manufacturers’ data sheets and BS 6150 / BS 8000-12. Check prices and VAT with your own records and HMRC.