Anti-Mould Paint UK 2026: Zinsser, Dulux, Ronseal Compared

Anti-mould paint is an emulsion that carries a dry-film biocide, so mould struggles to grow on the paint itself; it does not kill mould rooted in the plaster, and it does nothing about the condensation that feeds it. In the UK the specialist choices are Zinsser PermaWhite (often written Perma-White: self-priming, matt or satin, white or tinted, with a film designed to resist cracking, peeling and blistering for up to 7 years) and Ronseal 6 Year Anti Mould Paint (white, matt or silk, sold as keeping surfaces mould free for up to 6 years). The decorative alternatives are the bathroom emulsions from Dulux (Easycare Bathroom, five years' protection of the paint against mould), Crown and Johnstone's, and Farrow & Ball's mould-protected Modern Emulsion. Whichever you buy, the order of work decides the result: fix the moisture first (in England, Approved Document F asks for 15 litres per second of extraction in a bathroom), kill and remove the existing mould, let the wall dry, then apply two full coats and put nothing on top.

Claims and figures come from the makers' product pages and data sheets, read on 28 October 2026; Johnstone's website blocks automated checks, so its paint appears without figures.

What anti-mould paint actually does

Many water-based paints contain an in-can preservative that stops them going off in the tin. Anti-mould paint adds a second biocide meant to stay in the dried film and stop mould colonising its surface. Zinsser's UK data sheet says PermaWhite contains a biocide that protects the dried coating against fungal degradation, and names it: 4,5-dichloro-2-n-octyl-4-isothiazolin-3-one (DCOIT), at 0.12% by weight.

That naming is a legal requirement. Under the GB Biocidal Products Regulation, a paint that intentionally incorporates a biocidal product is a "treated article", and HSE's guidance on treated articles says that once a seller claims a biocidal property, such as protection against mould, the label must say the article incorporates biocidal products, state the property where it is substantiated, and name every active substance. The data sheet is the first place to look when two tins make similar promises.

Two consequences follow. The biocide protects the paint film, so it cannot reach mould growing in the plaster behind it. And it works at the surface, which is why Zinsser and Ronseal both say that painting over their anti-mould paint stops it working: it has to be the top coat. The claims differ too: only Ronseal and Dulux put a period on mould protection itself.

Zinsser Perma-White: 5 years or 7 years?

Both numbers circulate, and both come from Zinsser's UK distributor, Tor Coatings. They are not the same promise.

The current UK data sheet, linked from the PermaWhite Matt page on zinsseruk.com, covers the matt and satin versions. It lists the dry-film biocide, a film designed to resist cracking, peeling and blistering for up to 7 years before first maintenance, and a warranty that the contents are free of defects for three years from manufacture (PermaWhite technical data sheet). It puts no number of years on mould resistance.

An earlier data sheet, still hosted by some UK retailers (for example this copy at Decorating Warehouse), describes eggshell, satin and semi-gloss versions and guarantees the film against mould and mildew for five years when two coats are applied to the label directions. Read to the end, that guarantee is limited to replacing the paint or refunding its value, and painting over it voids it.

So the short answer: seven years is the durability target of today's PermaWhite film; the five-year mould guarantee belongs to the older sheet. Neither promises a clean wall whatever the room does. What the current sheet asks of you matters more:

• Two coats are required for the mould resistance, at 10 m² per litre per coat.
• Touch dry in 30 minutes, second coat after 2 hours, full cure in 7 to 10 days; no scrubbing for seven days.
• A dry wall, with a maximum moisture content of 16%, and air and surface between 10°C and 32°C at under 80% humidity.
• Bare plaster sealed first with a primer such as Bulls Eye 1-2-3, and mould stains blocked with a stain-killing primer-sealer such as B-I-N.
• Above tiles on shower walls, 24 hours before using the shower. Not for floors, shower enclosures, saunas, steam rooms or surfaces in prolonged contact with water.
• Tins from 1 to 10 litres, in white or tint bases mixed to BS 5252F, RAL and NCS colours.

UK anti-mould paints compared

The choice comes down to two questions: has the surface already grown mould, and do you want white? For a ceiling or cold corner that keeps going black, the specialist paints are built for the job, and Zinsser says PermaWhite's self-priming film bonds to gloss paint and tiles without sanding. For a well-ventilated bathroom that needs colour, a mould-protected decorative finish is usually enough: our guides to Dulux Easycare Bathroom and Johnstone's Bathroom paint list their ready-mixed shades, and our bathroom paint colours guide suggests colours by light and room size. Ronseal points anyone who wants a colour to its Anti Mould Clear Coat instead.

Find the cause first: condensation or damp?

The government's guidance for England sorts household damp into condensation, penetrating damp, rising damp and leaks, and warns that simply removing surface mould will not stop it reappearing (OHID, MHCLG and UKHSA, Understanding and addressing the health risks of damp and mould in the home, updated 1 April 2026). Paint helps with the first only, and only once the moisture is under control:

Condensation is physics you can put numbers on. The table gives the dew point of room air (FacadeColorizer calculation, Magnus formula): any surface colder than the figure gets wet.

At 20°C and 60% relative humidity, any surface below about 12°C collects moisture, and the wetter the air, the higher that threshold. In a British winter a window reveal, the inside face of a solid outside wall or the ceiling corner below a cold loft can drop under it, which is why mould appears there first and why the same corner fails again after a repaint. The government guidance lists the everyday levers: extraction, pan lids on, laundry dried outdoors where possible, internal doors shut while cooking and bathing, adequate heating, and a gap between furniture and external walls. Our guides to condensation problems and window condensation go further.

Ventilation: what Approved Document F asks for

In England, ventilation in new and altered homes is covered by Approved Document F; Wales and Scotland publish their own guidance. Volume 1 (dwellings, 2021 edition) opens with its reason: without adequate ventilation, mould and indoor air pollution can become a hazard to health. Its Table 1.1 sets minimum rates for intermittent extract fans:

It also asks for extract fans as high as practicable and no more than 400 mm below the ceiling, a manual override on any automatic humidity control and, in a room with no openable window, a run-on of at least 15 minutes after the room is vacated; with natural ventilation, every room with an external wall should have background ventilators such as trickle vents. When a kitchen or bathroom is refurbished, existing fans should be kept or replaced and checked (paragraph 3.30 of the 2021 edition of Volume 1).

These rules apply to building work, not to a room you are only repainting, but they are a fair benchmark: a bathroom fan that cannot shift 15 litres per second leaves the ceiling wet whatever paint is on it. Hold a sheet of toilet paper to the grille with the fan running; if it is not pulled firmly against it, clean or replace the fan before you decorate.

How to paint over mould, step by step

1. Fix the source. Repair leaks from the roof, guttering or pipes and sort out the extraction; Zinsser's guide to removing mould from walls starts there.
2. Protect yourself. Open a window, wear gloves and eye protection, and a suitable mask if you dry-sand, as the PermaWhite sheet asks.
3. Kill and remove the mould. The government guidance prefers mould and mildew products to bleach for health and safety reasons, although Zinsser's older sheet still suggested a bleach solution. Zinsser Mould Killer & Remover, Ronseal 3 in 1 Mould Killer or the fungicidal wash Dulux asks for all do the job; follow the label and let it dry.
4. Clean, rinse and dry. Degrease, rinse and let the wall dry fully; a moisture meter confirms PermaWhite's 16% limit.
5. Block stains, seal bare plaster. Mould leaves shadows that can show through emulsion. Zinsser's guide puts a water-based primer-sealer (B-I-N Aqua) over treated stains.
6. Apply two full coats. Respect the recoat time (2 hours for PermaWhite, 4 for Ronseal, 6 for Easycare Bathroom) and paint the ceiling too: warm, moist air rises and condenses on the coldest surface it meets.
7. Keep the steam away. Dulux asks for at least 24 hours before the room is exposed to condensation; Ronseal asks for 24 hours before showering or bathing, and so does Zinsser above tiled shower walls.
8. Leave it as the top coat. Never paint over it, and do not scrub PermaWhite in its first seven days.

Room by room: where it is worth paying for

• Bathrooms and en-suites. The classic case: the ceiling above the shower and the corner over an outside wall. A room with a history of mould suits a specialist paint; a well-ventilated one can take a coloured bathroom emulsion.
• Kitchens. Steam plus grease: a mould-resistant ceiling helps, and around the cooker a wipeable finish matters as much. Our Dulux kitchen paint guide compares the options.
• Utility rooms. Approved Document F asks for 30 litres per second here, double a bathroom, because washing machines, dryers and drying racks release a lot of moisture. See our utility room paint colours guide.
• Bedrooms on outside walls. Mould behind a wardrobe or bed head on an external wall is condensation. Pull furniture away from the wall and air the room in the morning before repainting; our bedroom paint colours guide has shades that can be tinted into a mould-resistant base.
• Conservatories and cold porches. Glass-heavy rooms swing between warm and cold; see our conservatory paint colours guide.

How much anti-mould paint you need

Worked example for a bathroom of 2.4 m by 1.8 m with a 2.4 m ceiling. The walls measure 20.2 m²; take off a door (about 1.6 m²) and 4.3 m² of tiling around the bath, and 14.3 m² is left, plus a 4.3 m² ceiling: 18.6 m² of paintable surface, or 37.2 m² for two coats.

Coverage figures are maximums on smooth, sound surfaces: porous or patched plaster takes more, and a stain-blocking primer is a separate purchase. A small en-suite with half the area fits in one 2.5 litre tin of any of the three. To hand the job over, our UK interior decorator cost guide covers day rates.

If you rent: painting is not the repair

In social housing in England, Awaab's Law has applied since 27 October 2025: landlords must investigate a potential significant damp and mould hazard within 10 working days and complete safety works within 5 working days of identifying one, and emergency hazards must be investigated and made safe within 24 hours (Shelter). Announcing the law, the government said it intended to extend it to private renting after consultation (gov.uk, 6 February 2025). Whoever owns the walls, report mould in writing with dated photos before anyone picks up a roller.

Solvents, biocides and indoor air

Under the VOC Regulations 2012, interior matt wall and ceiling paints (gloss up to 25 at 60°) are capped at 30 g of VOC per litre, glossier ones at 100 g/l. With a gloss of 18 to 23 at 60°, even PermaWhite Satin falls in the matt category, and Zinsser declares a maximum of 30 g/l; Crown says easyclean Bathroom contains at most 1 g/l. The biocide is a separate matter: a low-VOC tin can still be a treated article, so ventilate while painting and keep the data sheet that names the active substance.

Sources and references

• Zinsser UK (Tor Coatings), PermaWhite Matt and its technical data sheet: biocide, 7-year durability wording, coverage, drying, moisture limit, tinting, warranty, VOC.
• Zinsser, earlier Perma-White Interior data sheet, copy at Decorating Warehouse: five-year mould guarantee and its limits.
• Zinsser UK, Mould Killer & Remover and How to remove mould from walls: preparation sequence.
• Ronseal, 6 Year Anti Mould Paint, How to prevent mould with anti-mould paint and 3 in 1 Mould Killer: claim, finishes, coverage, drying, top-coat rule.
• Dulux UK, Easycare Bathroom Soft Sheen; Crown Paints, easyclean Bathroom Mid Sheen; Farrow & Ball, Modern Emulsion: mould claims, coverage, drying, sizes, VOC.
• HM Government, Approved Document F, Volume 1, 2021 edition: paragraphs 1.1, 1.20, 1.50 to 1.52, 3.30 and Table 1.1.
• OHID, MHCLG and UKHSA, damp and mould guidance (updated 1 April 2026): types of damp, mould products rather than bleach, moisture control.
• HSE, Treated articles: GB BPR definition and labelling.
• legislation.gov.uk, VOC Regulations 2012, Schedule 2: VOC limits.
• Shelter, How Awaab's Law changes the rules (October 2025), and gov.uk announcement (6 February 2025): start date, timescales, scope.
• Dew points and quantities: FacadeColorizer calculation (Magnus formula; makers' coverage figures), 28 October 2026.