Sign of damp
Ceiling patches
A yellow, brown or grey stain on the ceiling, often roughly round with darker rings at the edge. It may sag, bubble, drip after use of the bathroom above, or show salts and flaking putty. In top-floor flats patches often run along beams or near the edges of the room.
What it might mean in a flat
Stains and damp areas on the ceiling.
A ceiling patch almost always means water is coming from the floor above or the roof. If it sits under the bathroom of the flat above, that bathroom is the likely source and the fix usually happens in someone else's flat. In a top-floor flat the terrace is the first suspect. Patches that grow after rain point to the roof or external wall; patches that grow after someone upstairs bathes point to the bathroom.
Common causes
- Failed waterproofing under the bathroom floor of the flat above, letting shower and floor-wash water through the slab
- A leaking floor trap, nahani trap or WC connection in the flat above
- A concealed supply or waste pipe in the floor or wall above
- Terrace waterproofing that has cracked or lifted, on top-floor flats
- A blocked or leaking AC drain line or balcony drain above
What an inspection checks
How we confirm it.
- Meter readings across the patch and the surrounding ceiling against the dry reference, to map its full size
- Thermal scan of the ceiling, which often shows the damp area spreading along a beam or a pipe route beyond the stain, with each cool area confirmed by the meter
- Where the patch sits relative to the bathroom, kitchen, balcony or AC units of the flat above, or under the terrace
- Signs of past repairs: new putty, fresh paint only on that patch, or false ceiling panels
- Where access allows, a look at the floor trap, grout and fittings of the bathroom above
When to worry
Signals that it's active.
- The patch is wet to the meter, sagging or dripping
- It grows when the bathroom above is used, or after every heavy rain
- The plaster is crumbling or there are rust stains along a beam or slab soffit
- You are about to put in a false ceiling or lights that would hide it
Where it usually comes from
Questions buyers ask
The patch is under my neighbour's bathroom. Who fixes it?
Usually the leak is fixed in the flat above, at that owner's cost, and the damage below is made good afterwards. Many societies have bye-laws on leakage between flats, and they vary, so check yours. The report gives you the evidence to start that conversation.
The patch is dry now. Does that mean it is fixed?
Not necessarily. Many ceiling leaks are intermittent, wet after use of the bathroom above or after rain and dry in between. A re-scan in the season when it usually appears tells you more.
Can a thermal camera see through the slab?
No. It shows the surface temperature of the ceiling. A wet area cools as it evaporates, which shows up as a cooler patch, but cold pipes and air movement can do the same. That is why every cool patch is checked with a meter.
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