Exterior paint on coastal homes: preparation that makes it last

On the coast, exterior paint has a hard life. Salt, sun, wind and winter rain all attack it. We often see houses repainted every few years because the paint is peeling, chalking or blistering. In almost every case, the problem is not the paint but the preparation.

Why paint fails

Salt on the surface. Salt deposits on walls attract moisture and prevent paint from bonding.
Damp walls. Paint applied to walls that are wet, or that have moisture coming through them, will blister and peel.
Cracks. Water gets in through cracks, gets behind the paint and pushes it off.
Chalky surfaces. Old paint that has broken down to a powder will not hold a new coat.
Wrong products. Interior or low-grade paints used outside do not last.
Painting in the wrong weather. Paint applied in cold, damp or very hot conditions does not cure properly.

Preparation, step by step

Fix the causes of damp first. Repair gutters, downpipes, flashings and waterproofing, and deal with rising damp (see why homes get damp).
Wash the walls. High-pressure cleaning removes salt, dirt and loose paint. On the coast, this step is essential.
Remove loose and flaking paint by scraping or sanding back to a sound surface.
Treat mould and algae with a suitable fungicidal wash.
Repair cracks. Rake out and fill with a suitable exterior filler. Fine cracks can be treated with a crack-bridging system. Structural cracks need an engineer (see cracks in walls).
Let the walls dry completely before painting.
Prime. Use the correct primer or sealer for the surface: bare plaster, chalky old paint, or previously painted walls all need different products.

Choosing paint

For coastal homes, choose a good-quality exterior paint designed for harsh conditions. Elastomeric and high-build coatings bridge fine cracks and stretch with the movement of the building. Ask the manufacturer for a specification for your situation, and follow it, including the number of coats.

Metalwork and timber

Steel balustrades, gates and window frames need their own system: rust removal, a suitable primer and an enamel or specialist coating. Exterior timber needs a breathable timber finish rather than ordinary paint.

Timing

Paint in dry, mild weather. In Cape Town, late spring and autumn are usually best. Avoid painting in the heat of a summer afternoon, during a strong south-easter that dries the paint too quickly and blows dust onto it, or in winter, when walls rarely dry out.

Maintenance

Wash down exterior walls once a year, especially on the side facing the sea. Touch up damaged areas before water gets behind the paint. A well-prepared paint system with regular care should last many years, even on the coast.

We repaint houses as part of our renovations, with the preparation done properly. If your house needs a repaint, get in touch.