Damp on a UK wall is a word that covers three different jobs. Condensation after cooking or a bath is mostly air and heat. A leak is water that already had a pipe or a tank. Weather getting through a roof, a gutter or a failed pointing line is a building or roofing visit. Treating all three as “get a damp-proof course” wastes a week and the first call.
This guide is a sort, not a survey. It will not tell you the moisture reading a specialist would take, and it is not a quote. If you already know the ceiling is dripping, open plumbing or roofing on the directory.
Look once, write three facts
Before you wipe anything, note the room, the height of the mark, and the last weather. A patch on an outside wall after rain is a different story from beads of water on a cold window in a closed bathroom. A stain on a ceiling under a bathroom is a third story again.
| What you notice | Often means | First list to open |
|---|---|---|
| Black specks on cold corners, windows, or behind a wardrobe after showers | Condensation and poor air | Wait and ventilate; a builder only if it keeps returning on a solid wall |
| Brown ring on a ceiling under a bathroom or tank | A leak above | Plumbing |
| Stain that darkens after rain, under the eaves or at a chimney | Weather getting in | Roofing or building |
| Water on the floor, a hiss, or a meter that spins with taps off | An active leak | Plumbing, today |
The table is a start, not a diagnosis. A single cold wall in an old terrace can show both condensation and a failed gutter. If two rows fit, say both on the phone.
When waiting and wiping is still reasonable
If the mark appears after baths, cooking or drying clothes indoors, and it fades when you open a window, start with air. Use the extractor, leave a gap under the door if the fan needs it, and move furniture a hand’s width off an outside wall. Wipe with a dry cloth. Do not start on bleach as a first step on plaster you have not identified.
Give that a few days of ordinary weather, not a week of locked windows. If the specks stop spreading, you may not need a trade at all. If they keep returning on the same cold corner in a room you already ventilate, a builder or a decorator may need to talk about insulation and plaster — that is no longer a wipe.
When it is a plumber
Look at the room above. A bathroom, a cylinder cupboard, or a radiator on the floor over the stain is a plumbing first call. Check the stopcock location before you panic: if water is running, shutting the mains is the homeowner move, then the phone. Do not chase a leak into a live consumer unit or a soaked rose. Water on electrics is an electrician after the water is stopped, not a damp-proof cream.
A boiler that has been topped up every day can also feed a silent leak. That belongs with the boiler-pressure guide and a Gas Safe engineer if the appliance is involved.
When it is the roof, the gutter or the wall
If the patch tracks last night’s rain and sits under the eaves, a valley or a chimney, do the ground-level look in the seasonal roof check. A gutter that overflows will wet the same brick line for months and look like “rising damp” in a Facebook photo. It is not. Clear what you can reach safely; leave height and the covering to a roofer.
A tide mark at skirting on a solid ground-floor wall, with crumbling plaster and a musty line, is the one case where people jump to a chemical damp course. That can be a builder’s visit, and it can also be a blocked gully or an internal leak. Do not buy a kit from a van before someone has looked at the outside ground level and the rainwater goods.
When to stop sorting and call
- Water is running, dripping, or the ceiling is bowing.
- You can hear a pipe or see the meter move with every tap shut.
- The stain grew across a whole wall after one front of weather.
- Electrics are in the wet area — switches, a rose, a socket.
On the call, say the room, the height, the weather, and whether you shut the water. Ask who is coming — plumber, roofer or builder — and whether the first visit is to find the water or to quote a repair. Use the cost notes only as a briefing. This site does not honour a figure and does not email the business.
City lists sit under each trade. Tenants should tell the landlord the same three facts; a listing is still the number you dial if you have been asked to get someone in.
Pick the list that matches the water
Plumbing for a leak above. Roofing for weather. Building if the wall itself is the job. You place the call.