Balcony leaking into the flat below
A balcony is a small external slab directly above occupied space, usually with a door threshold on one side. The two recurring faults are a fall running back toward the door instead of away, and a threshold upturn that is too low.
Not an emergency, but it will get worse and more expensive with every monsoon it survives.
Probable causes, ranked
Ordered by how often we find each one to be the actual source. The 'tell' is what distinguishes it from the others.
- 01most common
Fall running toward the building rather than away
The tell — Water collects at the door threshold after rain.
Terrace Waterproofing → - 02common
Waterproofing upturn at the threshold too low
The tell — Damp appears inside the room at the door line.
Bathroom Waterproofing → - 03common
Blocked or absent balcony drain
The tell — Standing water across the whole balcony after rain.
Terrace Waterproofing → - 04less common
Railing fixings drilled through the barrier
The tell — Staining below lines up with railing post positions.
Refuge Area Waterproofing →
Sixty seconds, before you call anyone
- Photograph it while it is actively wet. A dried stain tells a surveyor far less than a running one.
- Note whether it worsens with rain or with usage. Rain-linked points to the building envelope; usage-linked points to plumbing. This single distinction settles most arguments about responsibility.
- Check the area directly above and beside the damage, not only below it. Water travels along a slab before it drops.
- Look specifically for the tell of the most likely cause: water collects at the door threshold after rain.
- Do not chip into saturated plaster or paint over a damp patch. The first risks bringing material down; the second destroys the evidence needed to trace the path.
What it becomes if you leave it
Small in area but directly above a habitable room, so it is a persistent nuisance. Continuous wetting of a thin cantilever slab also corrodes reinforcement in a section with very little cover to lose.
Often seen alongside this
- Cracked or falling chajja and projection
A chajja is a thin cantilever with minimal concrete cover, so its reinforcement corrodes earlier than anywhere else on a building.
- Refuge floor leaking into the flats below
A refuge floor is an exposed slab sitting directly above occupied flats, so any failure shows up below almost immediately.
- Water entering around a window frame
Water at a window is usually entering at the junction between frame and wall rather than through the window itself.
Balcony leaking into the flat below — questions we get asked
What is the most likely cause of balcony leaking into the flat below?
Fall running toward the building rather than away. The sign that points to it is: water collects at the door threshold after rain. That said, the ranking here is a starting point — the actual source is confirmed by survey, because more than one of these can be true at once.
What happens if I leave it?
Small in area but directly above a habitable room, so it is a persistent nuisance. Continuous wetting of a thin cantilever slab also corrodes reinforcement in a section with very little cover to lose.
Can I diagnose this myself before calling anyone?
Partly, and it is worth doing. Photograph it while it is actively wet, note whether it worsens with rain or with usage, and check the area directly above and beside the damage. That single rain-versus-usage distinction narrows the cause more than anything else you can do in sixty seconds.
How urgent is this?
Act this season. Not an emergency, but it will get worse and more expensive with every monsoon it survives.
Send us a photograph and we will tell you what we think it is
WhatsApp a photo taken while it is wet, with a note on whether it tracks with rain or with usage. That is usually enough for a first opinion, and the site inspection that follows is free.
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