How to paint exterior walls
Updated: 23 October 2026
You are looking at a sound rendered wall, or one that has already been painted, and you want it finished before the weather turns. How to paint exterior walls, for that job, is a sequence: get the face clean and dry, stabilise it only if it is powdery, then put on two coats inside the tin’s weather window. Which tin to buy is the [facade paint comparison](/hub/paints-and-varnishes/facade-paint). Peter F. updated this page on 23 October 2026. Our links may earn a commission at no extra cost to you.
You are looking at a sound rendered wall, or one that has already been painted, and you want it finished before the weather turns.
You are looking at a sound rendered wall, or one that has already been painted, and you want it finished before the weather turns. How to paint exterior walls, for that job, is a sequence: get the face clean and dry, stabilise it only if it is powdery, then put on two coats inside the tin’s weather window. Which tin to buy is the facade paint comparison. Peter F. updated this page on 23 October 2026. Our links may earn a commission at no extra cost to you.
Our top picks
| Badge | Product | Touch-dry | Pack | Water claim | Note | Price | Offer |
|---|---|---|---|---|---|---|---|
| Best overall |  Sandtex Sandtex Ultra Smooth white 2.5 l | 1.5 hours | 2.5 litres | Waterproof | 9.4 | about £15.95 | View offer |
| Alternative |  Leyland Leyland Granocryl white 2.5 l | 24 hours | 2.5 litres | Conflicts | 9.2 | about £15.17 | View offer |
| Best value |  Dulux Dulux Weathershield white 7.5 l | 4 hours | 7.5 litres | Waterproof | 9.2 | about £32.52 | View offer |
On this page
Make the wall fit to paint
Start at the top and deal with whatever is loose, green or damp before you open the tin. Brush off dust, flaking paint and friable grains. If algae or mould is staining the render, use a fungicidal wash and let the wall dry. A hard blast from a pressure washer is a poor default on old render, and the wrong tool if the face might be asbestos cement. Dash quantities are a separate sum on painting pebbledash.
Fill cracks that are stable, and leave hollow or blown patches until they are repaired. Mask sills, pipes and glass, and keep the film off the damp-proof course and off air bricks. A wet wall will not take the film evenly.
Primer only if your hand comes away dusty
Rub the dry render with your hand. If the palm stays clean, you do not need a stabilising solution. That sealer is for chalky or friable faces. A sound wall gets the masonry paint itself. Dulux Trade’s smooth sheet, not the 7.5 litre amazon tub, says you can thin the first coat about 1:5 on new bare sound surfaces, and use stabiliser only if the face is still powdery. When that sealer belongs is in the masonry paint buying guide.
Sealing a hard wall can hold moisture in the render. None of the eight listings answers the primer question, so the tin you opened still wins. A white, chalky palm wants a masonry stabiliser, cured as that product asks, then paint.
Two coats, from the top, in a dry spell
Cut in with a brush, then roll from the top down so spatters land on unpainted render. Two coats is the pattern on Dulux’s consumer page and on Sandtex’s exterior guide, Stir until the colour is even. HQC reviews often say the shade is missing until that stir is a long one.
Dulux’s consumer page says dry conditions, above 10°C, and about 4 hours between coats. The Trade sheet says not below 7°C, and not in rain or humidity above 80%. Sandtex’s smooth page is about 8°C and a recoat around 3–4 hours. On these listings, Dulux’s dry-time field is 4 hours and Leyland’s says 24 hours while full cure says 4 hours. One Leyland reviewer reported a patio coat washed off by overnight rain.
When you should not carry on
Stop if a garage roof or a wall panel might be asbestos cement. The Health and Safety Executive’s a16 guidance says you do not sand it and you do not use aggressive preparation that releases fibres. Stop as well if render sounds hollow, if cracks are moving, or if the ladder is not safe.
In England, ordinary exterior painting can be permitted development, and that does not switch off listed-building consent or an Article 4 direction. Scotland is not covered by the English class. A short pick, once the wall is fit to paint, is best exterior masonry paint.
Common questions
How do I paint an exterior wall?
Wash off dirt and green growth, let the wall dry, fill only stable cracks, then apply two coats of exterior masonry paint from the top in a dry spell. Use a stabiliser only if the face is still powdery after brushing. Keep the film off the damp-proof course. If the surface might be asbestos cement, or the render is hollow, stop and get advice before you prep it.
How many coats of masonry paint?
Two coats is what Dulux’s consumer page and Sandtex’s exterior guide specify. A review that managed one coat on a similar colour does not replace that. The first coat can be thinned on new bare sound render if the product sheet says so. A second coat is what evens porosity and gives the film the maker calculated the coverage for.
How long should I wait between coats?
Use the tin you opened. Dulux’s consumer Weathershield page says about 4 hours, above 10°C, in the dry. The Trade sheet’s floor is 7°C and it also limits high humidity, and those two Dulux lines are not the same product wording. Sandtex’s smooth page is around 3–4 hours and about 8°C. Leyland’s amazon fields disagree with each other at 24 hours and 4 hours, so do not pick the shorter one because you are in a hurry.
Can I paint if rain is due tonight?
Not if the film will still be fresh when the rain arrives. Masonry paint needs a dry wall and a dry window after you finish, and a waterproof claim is not a licence to paint in a shower. One review in the Leyland file described a patio coat gone after overnight rain. If the forecast is wet before the recoat time on your tin has passed, wait for the next dry day.
What if the wall is green?
Treat the algae or mould with a fungicidal masonry wash and let the wall dry before any paint. Painting over live growth is a usual reason for the new coat to fail. A wipe that leaves a green stain is not a treatment, and a stabiliser is only for a face that is also powdery.
What if I think the garage is asbestos cement?
Do not sand it, scour it or pressure-wash it. HSE a16 is the UK note on asbestos cement sheet, and aggressive prep is how fibres get into the air. If the sheet is damaged, or you are unsure, get competent help rather than experimenting with a roller.
When should a decorator take over?
Call someone when the render is hollow or cracked in a way that moves, when you would be working at height without safe access, when the building is listed, or when the surface may be asbestos cement. A sound ground-floor render in a dry week is the DIY case these tins are sold for. Two-storey pebbledash with loose stones is the case that stops being a weekend plan.
Related pages
Sources
Public sources from the research digest, last checked on 22 October 2026. Shelf prices and star lines are the amazon.co.uk figures in the display file. The price band is this set, not a market average. No listing was lab-tested. The Dulux Trade sheet is not the same listing as the 7.5 litre tub.
- VOC in Paints, Varnishes and Vehicle Refinishing Products Regulations 2012, Schedule 2 (retrieved 22 October 2026)
- GPDO 2015, Class C, exterior painting (retrieved 22 October 2026)
- Richmond upon Thames conservation areas FAQ (retrieved 22 October 2026)
- HSE a16: painting asbestos cement (retrieved 22 October 2026)
- Dulux Weathershield smooth masonry paint (retrieved 22 October 2026)
- Dulux Weathershield FAQs (retrieved 22 October 2026)
- Dulux Trade Weathershield smooth masonry paint data sheet (retrieved 22 October 2026)