Summer storms can drop a lot of rain in a short time. If a damp patch appears on an inside wall or ceiling afterwards, the cause is usually penetrating damp: water getting in through a defect in the building.
Signs of penetrating damp
- Damp patches that appear or grow after heavy rain
- Patches at any height, not just near the floor
- Staining around windows, chimney breasts or below roof valleys
- Blown or bubbling plaster and peeling paint in one area
What to check outside
Gutters and downpipes
Blocked gutters overflow straight down the wall, and cracked downpipes can soak brickwork for hours. Look for staining, moss and green streaks on the outside wall.
Pointing and render
Eroded mortar joints and cracked render let rain soak into the wall. Hairline cracks in render can draw water in and trap it.
Windows and doors
Failed sealant, blocked drainage holes and sills without a drip groove all let water run back into the wall.
Roofs, chimneys and parapets
Slipped tiles, cracked flaunching, failed lead flashings and parapet walls are common sources of damp at high level.
Why damp proofing injection won’t fix it
A chemical damp proof course stops ground moisture rising up a wall. It does nothing to stop rain getting in through a defect higher up. Penetrating damp is fixed at source by repairing the defect, then letting the wall dry and replastering where needed.
Getting it diagnosed
Some defects are easy to spot; others need a closer look. Our surveyors check the outside of the building as well as inside, and our property maintenance team can carry out repairs such as repointing, render repairs and gutter work.
Read about our damp proofing and property maintenance services.
