Leaking Lean-To Windows

[greenceb]

Hi all,

Moved into a terraced house a couple of years ago with a lean-to extension at the back (which was built a number of years ago). There are roof windows for half of the extension that, when the rain gets bad, cause a slight leak inside the house from the external wall. There’s a box gutter behind the windows and, when that gets full (in particularly bad rain), the leak gets worse.

Last year’s solution was to put some waterproof tape over the end of the window which has significantly helped. To prep for this year, I was planning on replacing last year’s tape with some more heavy-duty butyl sealant tape, but thought I’d see if anyone could advise on best solution for sorting the problem before ordering the tape.

Thanks! Appreciate any advice!

 

[RandomGrinch]

Hi,

I'm only a DIY'er, so feel free to ignore!
I believe your roof needs sorting out properly by a suitably skilled roofer.
The only suggestions I can make to keep you going are just bodges!
I have found flash band to be really useful to help seal leaks:
https://www.screwfix.com/p/bostik-flashband-grey-10m-x-100mm/57969
Just make sure the area to tape is dust free. If you can pre-warm the tape (or lay it on a warm day), it will stick to most surfaces surprisingly well.
I've also used roof and gutter sealant:
https://www.screwfix.com/p/no-nonsense-roof-gutter-sealant-black-310ml/67521
This creates a decent waterproof seal that will remain flexible.
It is messy to use though, so make sure you mask up the areas to seal first, and use gloves to apply!
Personally, I think I would use both methods. Sealing the gaps first, and then running flashband over the edge of the windows and into the box gutter.
I hope that makes sense.
Good luck

 

[Mr Chibs]

What Size is the overhang of the glass panels into box gutter?

I’ve just finished building a lean-to and the roofing panels should have drip bars on them, and end caps on the ends of the rafter bars.

Perhaps rain is being blown back By the wind and in Through gaps in your roof.