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Leak from balcony guttering? How to fix?

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12 Jun 2025
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Hi all, really hoping for some advice.

We’ve had a leak in the corner of our living room ceiling that’s ruined the plaster and cornicing. Our estate agent thinks it’s coming from the balcony above - there’s a single drainage hole that leads into guttering, and they believe water’s getting in there.

They’ve said we need to reseal around the drain and paint the balcony floor with some kind of waterproof coating.

The balcony isn’t tiled - just a plain surface (possibly concrete) with one drainage hole.

Can anyone advise:
  • Does this diagnosis from the estate agent seem accurate? Or could it be a roofing issue?
  • What products (sealant/seal?) to use around the drain and what I should be doing?
  • What’s the best kind of waterproof coating or paint for the floor?
I’ve included photos of:
  • The balcony from above, below and from the front
  • The damaged corner in the living room
  • The entrance porch ceiling, which is also showing signs of water damage
Thanks in advance!!
 

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Why are you asking an estate agent for advice? Is this rented? If yes it’s down to your landlord to repair, not you (unless you are the landlord). Acrypol or similar may work.
 
Yes, there is obviously water ingress somewhere around that balcony or maybe even from the region above and around the bay window area, but I would be more interested as to how the joist ends have suffered from the ingress. If it's your own property then seek advice from a reputable surveyor, or if a tenant then it's all down to your landlord to rectify.
 
Just to clarify: I own the property and we’re hoping to move, so we’re currently trying to sell it. That’s why the estate agent got involved - they gave their suggestion based on what they could see during the initial valuation. I completely understand they’re not experts, which is why I’ve come here to ask for more informed advice.

The area I live in is a bit rough and when we first moved in we hired a local roofer who sadly turned out to be a cowboy - so I’ve been wary of getting more tradespeople involved without doing some homework first. I was hoping this forum might have some people with experience who could offer advice without the pressure or agenda of trying to land a job like a tradesman would.

I’m mainly trying to figure out:

Whether resealing around the drain and applying a surface coating is likely to solve the issue,
And what specific products would work best on a plain concrete (or similar) surface.

I appreciate the point about joist ends and water paths too - I’ll definitely take a closer look there. Thanks again for the help.
 
Th OP's username checks out!
But they did use a apostrophe correctly!

Whether resealing around the drain and applying a surface coating is likely to solve the issue,
It looks to be a reasonable and easy approach to apply; seems like you have plastic drain pipe with concrete poured around it which isn't going to make for a very enduring seal. Consider embedding a pre formed drain outlet in a compatible sealant (eg a TPE or steel one should stick to acrypol) and then acrypol over the top

Make sure the surface is clean and dry; looks like a bit of maintenance(jetwashing) is in order on that balcony. If you decide to forego using a formed outlet, grind the top edge of the hole to give it a slight radius, as it presently looks to be quite sharp in places and that will naturally form a weak point in any surface sealant you apply
 
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Hi all, really hoping for some advice.

We’ve had a leak in the corner of our living room ceiling that’s ruined the plaster and cornicing. Our estate agent thinks it’s coming from the balcony above - there’s a single drainage hole that leads into guttering, and they believe water’s getting in there.

They’ve said we need to reseal around the drain and paint the balcony floor with some kind of waterproof coating.

The balcony isn’t tiled - just a plain surface (possibly concrete) with one drainage hole.

Can anyone advise:
  • Does this diagnosis from the estate agent seem accurate? Or could it be a roofing issue?
  • What products (sealant/seal?) to use around the drain and what I should be doing?
  • What’s the best kind of waterproof coating or paint for the floor?
I’ve included photos of:
  • The balcony from above, below and from the front
  • The damaged corner in the living room
  • The entrance porch ceiling, which is also showing signs of water damage
Thanks in advance!!
Messy. Fussy.

There could be any number of reasons for the leak, including something as innocuous as a poorly sealed UPVC frame. A lot of head scratching required there unless there is anything obvious visible. I think if it were my issue, I'd start experimenting with various protective measures to see if I could eliminate items from my enquiry.
 
OP,
Your balcony could be silently rotting away hidden from view in the concrete.
Any re-bar could be rusting and swelling - cracks could be allowing moisture to enter the concrete - the concrete could have moved away from the wall?
How is the balcony supported - by projecting joists or by the brackets below?

Water is penetrating via the balcony into the building - there's a possibility of dry rot in the ceiling joists.
You could lift a couple of boards in the living room above & examine things?
Do all the houses on your block have similar balconies or is yours a one-off?
If its a one-off then think about having it removed?

The thing is that RICS surveyors are alert to balcony dangers due to leaks, & your balcony might be red flagged during any mortgage survey?
 
Worthy point; could have been base drained into or onto the sill, but all exits siliconed up and now frame water escapes via the sill ends or end caps and into the wall
 
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