How to paint exterior masonry

Video by Dulux UK. This walk-through is based on the video "How to paint your masonry - Dulux Weathershield" from the Dulux UK YouTube channel, which covers their step-by-step approach to getting a clean, weather-resistant finish on rendered and masonry walls. Worth watching before you pick up a roller — the prep sequence in particular is useful to see in action.

1. Check the weather forecast and pick the right day

Masonry paint needs dry conditions to go on properly and to cure once it is down. Aim for a dry spell of at least two consecutive days with temperatures above 5°C. In East Kent that window can be trickier to find than you might expect — the coast brings damp air even when it looks clear. Keep an eye on the BBC weather app for Sandwich rather than trusting a general South East forecast.

Avoid painting in direct scorching sunlight too. It sounds counterintuitive, but bright sunshine on a south-facing wall can cause the paint to dry too fast and leave lap marks. Early morning or an overcast but dry day is genuinely the ideal.

2. Clean the wall thoroughly

This is the step most people rush, and it shows later. Start by brushing down the whole wall with a stiff bristle brush to knock off loose render, cobwebs, and dust. Work from the top down so debris falls clear of areas you have already cleaned.

If there is any green algae, black mould, or lichen — common on older rendered houses in Kent, especially north-facing walls — treat it with a proprietary fungicidal wash first. Apply it, leave it for 24 hours, then scrub off the residue and rinse well with clean water. Painting over active algae just seals it in and the problem comes back within months. That said, if the wall is in genuinely good condition and just a bit dusty, a good rinse with a garden hose and a brush is fine.

3. Fill cracks and repair damaged render

Walk the wall and mark any cracks or holes with chalk so you do not miss any. Hairline cracks in a sound render are normal and can be filled with an exterior flexible filler. Rake the crack out slightly first with a filling knife or old screwdriver so the filler has something to grip, dampen the surface, then push the filler in and smooth it flush.

Larger areas of hollow or crumbling render are a different matter. Tap the wall with your knuckles as you go — a hollow sound means the render has parted company with the brickwork beneath and will need cutting out and re-rendering before you paint. There is no point in painting over render that is about to fall off. It depends on how bad it is, but this is the one thing that might push the job back a week if you find a fair bit of it.

4. Apply a stabilising primer if needed

Once the filler is dry, run your hand across the surface. If it comes away with a fine powder or chalk on it, the surface is too unstable to paint directly — the masonry paint will not bond properly and could pull away in sheets. In this case, apply a coat of stabilising primer first. It soaks into the surface, binds the loose particles, and gives the topcoat something solid to grip.

If the wall is sound and not powdery, you can skip the primer and go straight to the masonry paint, sometimes thinning the first coat slightly with water to act as a sealer on a new or bare surface. Check the tin instructions — they will tell you the correct mix ratio. Do not over-thin it; it is paint, not whitewash.

5. Apply the first coat of masonry paint

Use a wide masonry brush for cutting in around windows, doors, and soffits, then switch to a long-pile roller for the open wall areas. Work from the top down in sections, keeping a wet edge so you do not get join marks. Masonry paint is thick stuff and the roller will need reloading more often than you expect.

Do not try to get full coverage in one coat. A thinned-down or lighter first coat that soaks in is far better than a thick coat that sags or cracks as it dries. On a textured or rough render you will get through more paint than the tin suggests — always buy a little extra rather than running short and having to match a new tin later in the job.

6. Apply the second coat and finish the edges neatly

Allow the first coat to dry fully — usually four to six hours in decent weather, longer if it is cool or damp. Then apply the second coat in the same way. The coverage will be noticeably better and the colour will look even and solid once it is down.

Finish by going back around all edges with a brush: window reveals, the underside of sills, corners, and any spots the roller could not reach. These are the areas that catch the eye if they are patchy. Take your time on them. Mind you, do not overload the brush on vertical edges or you will get runs — three lighter passes beats one heavy one every time.

When to call a handyman

Call Richard if the wall is above single-storey height and you do not have suitable access equipment, if there is significant render repair needed before painting, or if you want the whole job done in a day without the faff. Exterior painting on a two-storey house really benefits from the right ladders and a second pair of hands to move them safely. Richard covers property maintenance across Sandwich and the surrounding East Kent villages — get in touch to talk through what needs doing.