A building announces a water problem months before the first drip. Paint changes, smells, salt blooms and hairline maps on the surface all say water is moving where it should not. Read them early and the fix is a repair; ignore them for two monsoons and it becomes reconstruction.
The eight signs, in rough order of urgency
1. A damp patch that returns
Dries in summer, reappears with rain: water has a path. The patch marks the exit, not the entry — the entry is usually higher and elsewhere.
2. Paint blistering or peeling in sheets
Moisture behind the film is pushing it off. Repainting without treating the moisture repeats the cycle at a fresh cost.
3. White salt bloom (efflorescence)
Water travelling through masonry dissolves salts and leaves them on the surface as white powder or crystals. It is the clearest possible statement that water is inside the wall.
4. Black spots and fungus
Persistent surface moisture grows mould, usually in corners and behind furniture, often with a musty smell arriving first.
5. A hairline crack map on a roof or terrace
Thermal movement cracks the surface; each line is a potential path. On an exposed slab this is the sign to act before, not after, the rain.
6. Hollow or lifting floor tiles above a damp ceiling
On terraces and bathrooms, water under the tiles debonds them. Tapping tells you the extent.
7. Rust stains bleeding from concrete
Water has reached reinforcement steel. This is structural, not cosmetic — bring in professional assessment.
8. A ceiling that actually drips
The final stage, not the first. Everything above happened earlier and was cheaper to fix.
What to do with a sign
- Photograph it — and the surfaces above and behind it.
- Find the water's likely source before choosing any product: roof above? bathroom behind? external wall taking rain? Our guide to telling dampness from leakage is the place to start.
- Treat cause, then symptom. The patch gets repaired last, after the path is closed — this is the whole logic of waterproofing chemistry.
Send your photographs with your city through the waterproofing page and we will tell you what we think is happening before anything is bought.
Frequently asked questions
The patch is small. Can it wait until after the monsoon?
The patch you see is the overflow of a path already full. Small is the cheap moment; the monsoon will enlarge it for free.
Can I just paint over a stain that has dried?
If the source is genuinely gone — a fixed pipe, a repaired roof — yes, after the wall dries through. If the source is unknown, paint is a bandage on an unexamined wound.
Which sign is the most serious?
Rust staining. Everything else is water damaging finishes; rust is water damaging structure.