Why has a stain appeared on my ceiling after the rain?

What is a ceiling stain?

It is a patch of ceiling in a different colour, usually yellowish, brownish or grey, sometimes with a defined edge, rings or small black dots. The colour is only the symptom: the cause is nearly always water that has soaked the plaster underneath.

Likely causes

Three causes are the most common:

1. Water coming from above. Slipped roof tiles, loose flashing, blocked gutters or cracks in the façade let rain in, and it runs down to the ceiling. Autumn is when many Portuguese roofs show their age, after a dry summer and the first heavy downpours.
2. A leaking pipe in the flat above. A water supply or waste pipe, for example in the bathroom upstairs, can soak the ceiling below even when it is not raining.
3. Condensation. Water vapour in the air meets a cold surface, such as a corner or a ceiling near a window, and settles there. It usually leaves a dark stain with small black dots. Many Portuguese homes have little insulation and no central heating, so cold surfaces are easy to find.

Mixed cases exist too, and old or blistered paint can muddy the picture. That is why we always say "likely cause", never certainty.

How to tell them apart

Each cause leaves a different clue:

• It grows or appears when it rains: points to water from above, from the roof or the façade.
• It grows even without rain: points to a pipe, especially if there is a bathroom or kitchen above.
• It gets worse on cold mornings with little ventilation: points to condensation, especially in corners or near windows, with small black dots.

If you touch the area and the plaster is wet, water is getting in right now. If it is dry and there is only a colour change, the water may have stopped and the stain may be old. Photograph the stain with the date: in a week or two, the comparison shows whether it is stable or growing.

What to do now

1. Photograph the stain close up and from a distance, and note the date and whether it had rained.
2. If water is dripping, protect the floor and furniture and move anything electrical out of the way. If the stain is near a light fitting or socket, do not use that fitting until an electrician (eletricista) has checked it.
3. If there is a flat above, ask the neighbours whether they have a plumbing problem.
4. Ventilate the room and see whether the stain improves or worsens over the next few days.
5. Do not paint over it until you know the cause: paint hides the stain, it does not fix it.
6. If you rent, tell your landlord (senhorio) in writing, with the photos, as soon as you see it.

When to call a professional

Call someone if the stain grows, if the ceiling goes soft or starts to sag, if it drips, or if the problem returns after drying. Who you call depends on the cause: a roofer (telhador) or builder (pedreiro) for water from above, a plumber (canalizador) for a leak, and a damp-proofing and ventilation specialist (técnico de isolamentos e ventilação) for condensation. If the ceiling is sagging or giving way, do not stand underneath it and ask for an urgent inspection.