Seepage on your wall? Do this before you spend a rupee on paint

Repainting over a damp wall is the most expensive shortcut in home maintenance. The patch always comes back, usually larger, and usually within one monsoon.

First, identify what kind of damp it is

• Rising damp starts at the skirting and climbs, with a tide-line edge and often salt crystals. Ground-floor flats and boundary walls.
• Penetrating damp shows as a defined patch high on a wall or ceiling, worst during and after rain. Usually a terrace, chajja or shared-wall failure.
• Plumbing leak stays wet regardless of weather and grows slowly and steadily.
• Condensation appears as black mould in corners and behind wardrobes, worst in winter, and is a ventilation problem, not a waterproofing one.

The tape test

Tape a 30cm square of plastic sheet tightly to the dry-looking wall next to the patch and leave it two days. Moisture on the wall side of the plastic means water is coming through the wall. Moisture on the room side means it is condensation.

What each one actually needs

Penetrating damp needs the source sealed — terrace membrane, chajja slope correction, or an external wall coating. Rising damp needs a chemical damp-proof course injected at the base. Plumbing leaks need a plumber, not a painter. Condensation needs airflow and often just an exhaust fan.

Then, and only then, paint

Let the wall dry fully after repair. In NCR that means two to three weeks in summer, longer in winter. Re-plaster if the old plaster has blown, apply a damp-resistant primer, and paint normally. Done in that order, the patch does not come back.