What a sunken bathroom is, and why it leaks
Most bathrooms in Andhra Pradesh apartments and houses are built with a sunken portion: the slab under the bathroom is dropped lower than the rest of the floor so pipes and the floor trap can run inside it. That recess is then filled, usually with brick bats or other filling, and tiled over.
The trouble is that the filling acts like a sponge. Any water that gets past the tiles, through worn joints, a cracked tile or the gap around a floor trap, soaks into it and stays there, sitting directly on the slab. Over months it finds its way through, and shows up as a damp patch on the ceiling of the room below or as a damp band on the wall of the room next door.
The usual entry points
When we open a leaking bathroom, the water has almost always come in through one of these:
- Worn cement joints between floor tiles, which absorb water straight through to the bed below.
- The gap around the floor trap and around pipes that pass through the slab, often never sealed.
- The corner where the floor meets the wall, which moves slightly and cracks.
- A cracked or hollow tile, especially near the shower area.
- A leaking concealed pipe or joint, which no amount of waterproofing on top will fix.
Signs it is the bathroom and not the terrace
Ceiling dampness on the top floor can come from the terrace; on lower floors in an apartment it is usually the bathroom above. A patch that appears or grows when the bathroom above is used, rather than after rain, points to the bathroom. So does a damp band at skirting height on the wall shared with a bathroom, or dampness that stays the same in dry months. If the patch only appears in the monsoon, read signs your terrace needs waterproofing as well.
How sunken area waterproofing is done
For a full treatment of an existing bathroom, the work runs in this order:
- The floor tiles and the filling in the sunken portion are removed, down to the bare slab.
- Every pipe opening through the slab is packed and sealed, because these are the usual way in.
- A rounded cove is packed around the floor-to-wall junction so no water sits in a sharp corner.
- Two waterproof coats are applied over the slab and carried up the walls to the required height, so splash water is covered too.
- Water is held in the sunken portion and checked before any filling or tiling goes back.
When you do not need to break the floor
If the water is only coming through the tile joints and has not yet collected in the sunken portion, epoxy grouting of the tile joints along with a surface treatment can stop it without opening the floor. Epoxy grout does not absorb water the way cement grout does. We will only recommend this when the site visit shows it will actually work; if water is already sitting in the filling, sealing the surface just traps it there.
How long the bathroom is out of use
For a full sunken area treatment, plan on about a week including drying and re-tiling. We do the waterproofing and coordinate with your mason for the tile work so the sequence is right. Once the leak is stopped, the damp ceiling or wall below needs time to dry before it is repainted; painting it straight away only traps the moisture. See wall dampness treatment for how we restore the wall.
Full details of the service are on bathroom and kitchen waterproofing.