Damp and salt on the walls: how it's properly treated

It's the call we get every winter: patches on the walls, paint peeling, a white powder along the skirting. Painting over it works for one winter. Then it comes back worse.

First, find where the water is coming from

• Rising damp — comes up from the ground. Leaves a horizontal line and white salt near the floor.
• Penetrating damp — comes in from outside: roof, facade, terrace or an open joint.
• Condensation — the most common in houses shut up part of the year. Shows in corners and behind furniture.
• A leak — a pipe failing inside the wall.

Each needs a different repair. Treating the wrong one is money thrown away.

The treatment that lasts

1. Fix the source — waterproof it, repair the pipe, ventilate.
2. Hack off the affected plaster back to brick, not just scrape the paint.
3. Let it dry. Weeks, not days.
4. Re-render with a renovation mortar that lets the wall breathe.
5. The right primer and a breathable paint.

Why it's worse in the Algarve

Strong sun, salt air, and houses closed up for months. South and west-facing facades take the most punishment — and are usually the first to show it.