How to Paint Masonry and Exterior Walls Properly
Practical steps for painting render, brick and pebbledash walls, from washing and treating algae to repairs, sealer, masonry paint and weather windows.
Exterior masonry paint protects walls from weather as well as changing how a house looks. Because it faces rain, sun, frost and algae, preparation and weather timing matter even more than they do inside.
Know your surface
- Smooth render or sand and cement. Takes paint well when sound.
- Pebbledash or textured render. Uses much more paint and needs thorough brushing.
- Brick. Once painted, it is difficult to return to bare brick, and painting can trap moisture if the wrong paint is used. Think carefully first.
- Previously painted masonry. Check for peeling, chalking and algae.
Do not paint over render that is crumbling, blown or hollow-sounding. Repair it first.
Check permissions
If you live in a conservation area, a listed building or a development with covenants, there may be restrictions on colour and finish. Check before you start.
Equipment
- Stiff brush, scraper, pressure washer or hose
- Fungicidal wash for algae, moss and mould
- Masonry filler or exterior filler
- Stabilising solution or fixing primer for powdery surfaces
- Masonry paint and appropriate brushes or rollers with long pile
- Masking and dust sheets for paths and plants
- Access equipment such as ladders, platforms or a scaffold tower
Working at height is a significant risk. If the job involves upper storeys, think seriously about hiring someone with the right equipment.
Step by step
1. Clean
Remove loose paint, dirt, moss and algae with a stiff brush and a wash. Pressure washing can be effective but use it carefully, since too high a pressure can damage render and force water into walls. Apply a fungicidal treatment if there is growth, following the instructions, and allow time to work.
2. Repair
Fill hairline cracks and holes with exterior filler. For larger cracks and damaged render, repair properly rather than painting over. Allow filler to dry.
3. Allow to dry
Masonry can hold moisture. Wait for walls to be thoroughly dry, often several days in settled weather.
4. Stabilise and prime
If the wall is powdery or chalky, apply a stabilising primer or fixing solution to bind the surface. New render may need a specific sealer. Check the manufacturer's guidance.
5. Protect
Mask windows, doors, pipes and fixtures. Cover paths, plants and ground.
6. Paint
Cut in edges first, then roll or brush the main areas, working from top to bottom in sections. Keep a wet edge to avoid lap marks. Two coats are normal, and the first coat can be lightly thinned if the manufacturer allows it.
7. Clean up and inspect
Remove masking while paint is still slightly tacky. Check from a distance in daylight for missed areas.
Weather and timing
Choose a spell of dry, mild weather. Avoid:
- Rain or heavy dew before or after painting
- Temperatures below the tin's minimum
- Direct hot sun, which makes paint dry too fast
- Strong wind that blows dust and debris onto wet paint
Late spring to early autumn is generally the best time. See paint drying and recoating times.
Common mistakes
- Painting over algae without treatment
- Painting damp walls
- Using interior paint
- Applying too thinly
- Ignoring cracks and failed pointing
- Painting brick with an unsuitable paint that traps moisture
Costs and hiring
Exterior work depends strongly on height and condition. If you want help, see cost to paint the outside of a house. Send photos of each elevation in your Compito request, mention storey height and surface type, and ask providers about access equipment and weather allowances.
Which masonry paint?
Masonry paints are made to be breathable, flexible and weatherproof, but products differ. Smooth finishes suit sound render. Textured or thicker versions are used to disguise hairline cracking and uneven surfaces. Some products are formulated to resist algae and moss for longer. Where the wall is old or has had moisture problems, ask a decorator or supplier which type suits the surface, and read the tin for the spread rate, since textured finishes use noticeably more paint per square metre.
A worked example
A semi-detached house with rough render needs noticeably more paint than a smooth surface of the same size. On a dry spring week, the sequence might be:
- Day 1: access equipment set up, wash down and apply fungicidal treatment.
- Days 2 and 3: leave to work and dry, fill cracks and repair loose areas.
- Day 4: stabilising primer where chalky, and cut in around windows and fascias.
- Day 5: first coat, with the second coat once it has dried.
Delays from rain are common, so allow slack in the plan.
Detail work
- Protect gutters, downpipes and windows with masking, and wipe splashes immediately.
- Paint under sills with a brush, since a roller leaves gaps.
- Check where render meets the damp-proof course and avoid painting over vents and weep holes.
- Leave air bricks and ventilation clear.
Flats, terraces and shared walls
Shared buildings often have a freeholder or management company that decides on colour and timing. Terraced homes may need neighbours' agreement if scaffolding crosses boundaries. Tell neighbours before work starts, especially if you need to use their side access.
Safety and when to call a professional
Ladders on soft ground, uneven paths and upper storeys are the main hazards. Anything above ground-floor level is usually best left to people with scaffolding or a tower and experience using it. Cracks wider than a hairline, bulging or hollow-sounding render, and persistent damp patches should be assessed before any paint goes on.
Frequently asked questions
Do I need to seal masonry before painting?
If it is bare, powdery or new, a stabiliser or sealer is usually recommended. Sound, previously painted walls often do not need it.
How many coats of masonry paint do I need?
Usually two, and more on rough or porous surfaces such as pebbledash.
Can I paint over peeling masonry paint?
Only after removing the loose paint and treating the surface. Painting over peeling paint will fail again.
Can I paint masonry in the rain?
No. Wait for a dry spell. Paint applied to wet walls will not grip properly, and rain soon after application can wash it off or leave streaks. Check the forecast for the drying period, including overnight dew and temperature drops.