How does anti-mould paint work?

Anti-mould paint contains fungicidal additives (biocides) that inhibit the growth of mould, mildew and algae on the painted surface. Most products use a combination of film-protecting biocides built into the paint film. The protection typically lasts 5-6 years. Anti-mould paint is not a cure for damp — it treats the symptom (mould growth) while you should also address the cause (condensation, ventilation, or moisture ingress).

Do I need to treat existing mould before painting?

Yes, always treat existing mould before applying anti-mould paint. First, apply a fungicidal wash (such as HG Mould Spray or Zinsser Mould Killer) and leave for the recommended time (usually 15-30 minutes). Scrub the area with a stiff brush, rinse, and allow to dry completely. If the mould has stained through, apply a stain-blocking primer before the anti-mould paint. Painting over existing mould without treatment will not stop it growing back.

What coverage does anti-mould paint give?

Most anti-mould paints (such as Zinsser Perma-White, Dulux Trade Anti-Mould, or Johnstone's Anti-Mould Acrylic) cover approximately 10-14 m² per litre per coat, with 12 m² per litre being a good average. Two coats are recommended for best protection. On porous or previously affected surfaces, coverage may be slightly lower. Always check the manufacturer's technical data sheet for the specific product.

Where should I use anti-mould paint?

Anti-mould paint is ideal for any room prone to condensation and moisture: bathrooms, en-suites, kitchens, utility rooms, basement rooms, and any walls or ceilings where mould has been a recurring problem. It can also be used in bedrooms where condensation occurs (for example, on cold external walls). Anti-mould paint is available in both brilliant white and a tintable base for coloured finishes.

How can I prevent mould from coming back?

Anti-mould paint helps, but you should also address the root cause. Ensure adequate ventilation — use extractor fans in bathrooms and kitchens (minimum 15 litres/second for bathrooms per Approved Document F). Maintain heating at a consistent level to prevent cold surfaces where condensation forms. Avoid drying clothes indoors without ventilation. Check for leaks, rising damp, or penetrating damp that may be contributing moisture. If the problem is persistent, consider a positive input ventilation (PIV) unit.

Anti-Mould Paint Calculator — How Much Anti-Mould Paint Do I Need?

Calculate anti-mould paint and fungicidal wash quantities for bathrooms, kitchens and damp-prone areas. Includes tin sizes and coverage for 2 coats.

Wall Height

Standard ceiling height is 2.4m

Wall Width

Average width per wall

Number of Walls

Number of walls to paint

Include ceiling

Ceilings in bathrooms and kitchens are often affected by mould

Ceiling Length

Ceiling Width

Existing mould present (needs fungicidal wash)

Mould must be treated with fungicidal wash before painting

Price Per Tin of Paint (optional)

Average price per tin for a cost estimate

How We Calculate This

This calculator estimates the quantity of anti-mould paint and fungicidal wash needed based on the area of walls and ceilings to be covered. It accounts for two coats of paint and recommends standard tin sizes.

The formula

Paint (litres) = Total area (m²) ÷ Coverage (12 m²/L) × Number of coats (2)

Fungicidal wash (litres) = Total area (m²) ÷ Coverage (5 m²/L)

Coverage rates

Anti-mould paint: 12 m² per litre per coat — 2 coats recommended
Fungicidal wash: 5 m² per litre — single application

Standard tin sizes

Anti-mould paint: Available in 2.5L and 5L tins
Fungicidal wash: Available in 1L and 5L containers

Preparation

If existing mould is present, it must be treated with a fungicidal wash first. Apply the wash, leave for the recommended time, scrub with a stiff brush, rinse, and allow to dry completely (usually 24 hours). Apply a stain-blocking primer if mould staining remains, then apply two coats of anti-mould paint allowing full drying time between coats.

Standards

Painting of buildings should comply with BS 6150 (Painting of buildings). Ventilation to prevent condensation and mould should comply with Approved Document F (Ventilation) of the Building Regulations.

Frequently Asked Questions

Last updated: February 2026

All calculations are estimates. Verify with your supplier.

Anti-Mould Paint Calculator — How Much Anti-Mould Paint Do I Need?

How We Calculate This

The formula

Coverage rates

Standard tin sizes

Preparation

Standards

Frequently Asked Questions

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