Source of seepage
Bathroom floor above
Water from the bathroom of the flat upstairs
How water travels
From the source to your wall.
Indian apartment bathrooms are stacked floor on floor, usually in a sunken or semi-sunken slab with a floor trap. When the waterproofing under the tiles cracks, or grout, the trap joint or the WC connection is not sealed, shower and floor-wash water soaks into the bedding mortar, finds a crack or joint in the slab and comes through to the ceiling below. From there it can spread along beams and down the walls of the flat below.
When it shows: All year, because it depends on bathroom use, not rain. It is often missed in the dry season only because a fresh coat of paint hides the stain.
The pattern it leaves
- A ceiling stain directly under the bathroom above, often strongest near the floor trap or WC position
- Damp spreading along the beam or down the wall shared with the bathroom below
- Patches that grow after the upstairs bathroom is used and dry in between
- Salts, bubbling putty or a soft patch on the ceiling of your own bathroom, kitchen or passage below
- Damp that does not change much with rain, which helps tell it apart from a terrace or external wall leak
How it's confirmed
Meter, thermal, eyes.
- Meter readings across the ceiling and upper walls against a dry reference wall, mapped onto the floor sketch to see whether the wet area matches the bathroom footprint above
- Thermal scan of the ceiling, ideally after the bathroom above has been used, to show a cool pattern spreading from the trap or WC position, with each cool area confirmed by the meter, since cold pipes can also show as cool
- Visual check of the bathroom above where the owner allows: grout, trap seal, WC base, slope and earlier repair marks
- A repeat reading after the upstairs bathroom is used, where that can be arranged
Who is usually responsible
It depends on where the water starts.
- Neighbour above
- Usually responsible for repairing a leak that starts in their bathroom, and in many cases for making good the damage below. Exact rules depend on the society's bye-laws, which vary.
- Society or association
- Often has a role under the society's bye-laws, which vary: some set out how leakage between flats is handled and who pays, and the society can help when the neighbour does not respond.
- Builder (within defect period)
- In a new building, a bathroom waterproofing defect brought to the builder's notice within five years from the date of handing over possession falls under Section 14(3) of the RERA Act, 2016. Your state's rules may differ.
- Owner
- Usually responsible for repainting and re-plastering inside their own flat once the leak above is fixed, unless agreed otherwise.
Typical repair approach
What a fix usually involves.
Described for understanding, not as a recommendation. Megahedge does not do repairs or recommend contractors.
- 01Re-grouting and sealing the floor trap, WC base and pipe entries in the bathroom above where the waterproofing below is still sound
- 02Where the waterproofing has failed, removing the floor tiles and bedding, laying a new waterproofing layer up the walls at the edges, and re-tiling with the correct slope to the trap
- 03Repairing or replacing a leaking trap, WC connection or concealed pipe found during the work
- 04Letting the ceiling below dry fully, which can take weeks to months, then re-plastering and painting it
- 05A re-scan after the repair to compare readings with the original ones
Questions buyers ask
My neighbour says the leak is not from their bathroom. What can I do?
A report that maps the wet area against their bathroom's position, with readings and thermal images, gives you something specific to show them and the society. Megahedge states the likely source as an opinion based on evidence, and the conversation is yours to have.
Can the leak be fixed from below?
Coatings on the ceiling below do not stop water coming through the slab. The leak usually has to be fixed in the bathroom it starts from.
I am buying a resale flat with a patch under the bathroom above. What should I ask?
Ask the seller whether the neighbour above has fixed their bathroom, what was done and when, and whether the patch has come back since. Asking for the repair before registration is easier than chasing it afterwards.
Find the damp before you pay for it.
Book a moisture and thermal inspection. Report on WhatsApp within 24 hours.