The ceiling patch under the bathroom above: whose problem is it?

In most Indian apartment buildings, bathrooms are stacked floor on floor. That keeps plumbing simple. It also means that when the waterproofing under one bathroom floor gives way, the water lands on the ceiling of the flat below. If you are buying a resale flat, the patch under the bathroom above is the single most common thing to check, and the hardest to settle once you own the flat.

How the water gets there

A bathroom floor has a sunken slab filled with brick bat or similar fill, a waterproofing layer, and tiles on top. Water that gets past the tiles, through open grout or a gap around the floor trap, collects in the fill. If the waterproofing below has cracked or was never continuous, it seeps into the slab and shows on the ceiling below as a ceiling patch, often with a brown ring or white efflorescence at the edge.

Leaks from concealed plumbing inside the wall or floor of the upper bathroom produce a similar patch, but tend to stay wet regardless of whether the shower is used. The full pattern is covered in our page on the bathroom floor above.

Signs that point to the flat above

• The patch sits directly under the upstairs bathroom, often near where the floor trap or WC would be.
• Walls around it are dry, so the water is coming from above rather than sideways.
• It gets worse after the upstairs bathroom is used heavily and does not follow the rain.
• Paint peels or bubbles in a rough circle, sometimes with drips or rust stains from the reinforcement in the slab.

Whose problem is it?

It depends on where the failure is, and on your state's society or apartment ownership law and your society's bye-laws. As a general pattern:

The difficulty is that the repair has to happen in someone else's home. The neighbour above needs to agree to their tiles being lifted, and that conversation is far easier before you buy, when the seller still has a reason to sort it out.

What to record before you talk to anyone

1. Date-stamped photos of the patch, from below and at an angle, with something in the frame for scale.
2. Its position relative to the room: distance from the walls, and which upstairs room sits above it.
3. When it gets worse: after rain, after the upstairs bathroom is used, or all the time.
4. Any written answer from the seller about past leakage and repairs.
5. Whether the society has a record of a complaint from this flat.

A dry patch with a stain is not the same as an active leak. A stain can be old, from a leak that was fixed years ago. What tells them apart is whether the area is still wet, and that is what a moisture meter reading against a dry wall in the same flat shows. A thermal camera helps map the extent, but a cool area is confirmed with a meter before anyone calls it damp. Our methodology page explains why.

If you are still deciding

You can ask the seller to get the upstairs bathroom repaired before registration, ask for a price adjustment that covers your share of the work, or walk away. Megahedge does not advise which. What helps in every case is evidence that names the likely source, so the seller, the neighbour and the society are all talking about the same thing.

WHO's 2009 guidelines on dampness and mould link damp homes with respiratory symptoms; speak to a doctor about health concerns.

A pre-purchase damp inspection records the readings and the likely source for every ceiling under a bathroom in the flat.