How to paint a rendered wall

Video by Wickes. This walk-through is based on the video "How to prepare and paint exterior surfaces with Wickes" from the Wickes YouTube channel, which covers the full preparation and painting process for exterior masonry. The emphasis on surface preparation before a brush or roller goes anywhere near the wall is the most useful part.

1. Check the weather forecast and pick your window

Masonry paint needs dry conditions to apply and a period of dry weather afterwards to cure properly. Aim for a run of at least two consecutive dry days with temperatures above 5°C — most paint manufacturers will specify something similar on the tin. Avoid painting in direct strong sunlight either, which can cause the paint to dry too fast and leave brush marks or lap lines.

In Kent, you can usually get a good painting window from late April through to September, though even summer can throw in a rainy week. Check the five-day forecast before you buy your paint, not the morning of the job. It sounds obvious, but it saves a wasted trip to the merchants.

2. Clean the surface thoroughly

A pressure washer is the quickest way to shift dirt, algae, and old flaking paint from rendered walls. Work from the top down and keep the lance moving — holding it too close or too long in one spot can damage soft render. If you do not have a pressure washer, a stiff-bristled brush and a bucket of warm water with a proprietary masonry cleaner will do the job, just more slowly.

Pay particular attention to any green or black algae patches. These need treating with a fungicidal wash rather than just rinsing off — if you paint over algae, it will grow back through the paint within a season. Apply the fungicidal wash as directed, leave it to work, then rinse it off before you move on. Allow the wall to dry fully before you do anything else.

3. Fill any cracks and loose areas

Go over the wall carefully and press your thumb into the render at different points. Any hollow-sounding or spongy patches mean the render has delaminated from the wall behind, and paint will not hold on top of it. These areas need hacking off and re-rendering before you pick up a brush. It is not a small job, but there is no point painting over a surface that is already falling off.

Fine hairline cracks can be filled with an exterior flexible masonry filler — press it in, smooth it off, and allow it to cure fully. For slightly wider cracks, rake out any loose material first so the filler has something to bond to. Do not use interior filler outside; it will absorb moisture and fall out within the first winter. Once the filler is dry, sand it back lightly so it sits flush with the render around it.

4. Apply a stabilising primer or diluted first coat

If the existing paint is powdery, chalky, or the surface is new render, apply a coat of stabilising primer before you paint. This binds the surface together and gives the masonry paint something solid to stick to. Skip it on a chalky surface and your top coat will peel away with the powder underneath it when it dries.

On a previously painted wall in good condition, you can instead thin your first coat of masonry paint with about 10 per cent water and use that as a primer. This soaks in and bonds without leaving a thick surface build-up that might crack. Read the tin first — some masonry paints specify a first coat dilution; others say apply neat throughout. Either way, two thinner coats beat one thick one.

5. Apply the masonry paint in even coats

Use a large masonry brush or a thick-nap roller for textured render, and a medium-nap roller for smooth surfaces. Work in manageable sections — a wall is not a ceiling; you are not racing against a wet edge in the same way, but you still want to keep a wet edge to avoid lap marks. On a big elevation, start at the top and work down so any drips fall onto unpainted surface.

Two full coats are standard. Allow the first coat to dry completely — usually four to six hours in good conditions — before applying the second. The second coat is what gives you the coverage and depth of colour, so do not rush it. On older pebbledash or heavily textured render, you may find a third coat is needed in places to get even coverage. That said, three thin coats will always outlast two thick ones.

6. Finish the edges and tidy up

Use a smaller 50 mm or 75 mm brush to cut in neatly around window frames, soffits, guttering, and any brickwork that is not being painted. Masking tape helps here, but be careful — leave tape on rendered surfaces in warm weather and it can pull the paint off when you remove it. Peel it back while the paint is still slightly tacky rather than waiting until it has gone hard.

Keep a damp cloth handy to wipe any splashes off glass or UPVC frames before they dry. Masonry paint bonds to plastic surprisingly well once it has cured, and it is a lot harder to remove than you might expect. A quick wipe while it is wet saves considerable effort later.

When to call a handyman

Call Richard if significant sections of render are loose, hollow, or cracked across a wide area — that is a re-rendering job rather than a painting job, and it needs doing first. Working at height on a two-storey or taller wall also calls for proper scaffolding or a tower, which most homeowners do not have. If you want the whole elevation done properly and safely in a day rather than a weekend of precarious ladder work, it is worth getting in touch.