The white house with blue shutters is a true picture: an Algerian façade takes the sun, sand-laden wind, salt air on the coast and the temperature swings of the high plateaus. A façade paint picked at random chalks within three years, blisters on a damp wall or cracks on a render that moves.
The choice is made by looking at the wall before looking at the colour chart. Three questions matter: what the render is made of, whether it is damp, and whether it is cracked.
Read the wall
Run your hand over the façade: if it comes away white, the old paint is chalking and must be brushed down and stabilised. Tap the render with the handle of a hammer: where it sounds hollow it has come away and must be hacked off and redone, or the new paint will leave with it.
Look for damp at the foot of the walls and under the window sills. Rising damp or a sill with no drip is dealt with before painting; no paint stops water coming from inside the wall.
Three families of paint
Acrylic façade paint is the most common: easy to apply, durable, available in every colour. It suits a sound, dry cement render. It is the right default for a recent house.
Siloxane paint combines an acrylic resin with a silicone binder: it sheds rain while letting the wall breathe, and stays cleaner. It is the one to use on the coast and on walls exposed to driving rain.
Lime render and limewash are made for old stone or solid-brick walls, which need to dry outwards. Covering an old wall with a paint that is too closed traps the damp inside it.
The preparation that makes it last
Pressure-wash the façade and let it dry for at least forty-eight hours. Fill fine cracks with filler; open the wider ones into a V before filling. Apply a stabilising primer on porous or chalky surfaces: it hardens the surface and evens out the absorption.
Protect the windows, the ground and the plants with sheets and masking tape. On a scaffold, work in full horizontal bands from the top down, to avoid visible lap marks.
How many litres?
A façade paint covers about 6 to 8 m² per litre per coat on smooth render, much less on a scraped or roughcast finish. Two coats are needed. For a 120 m² façade, allow around 35 to 40 litres — three 15-litre buckets to be safe. The paint calculator works it out in whole buckets for your surfaces.
The right moment
Paint between 8 and 30 °C, never in full afternoon sun or high wind, nor when rain is forecast within twenty-four hours. In spring and autumn, start with the wall that was in shade in the morning.
For the traditional white and the blue shutters, keep the same bucket from one coat to the next and mix two buckets together before you start: the colour will stay the same across the whole façade.
