Rain = leaking roof/dormer

Hi

Have had a leak into our 1st floor bathroom for several months, but we haven't managed to catch in the act over the summer - everything has looked dry when we 've gone up to the converted loft.

Lots of rain today and the bathroom ceiling is dripping through - and a give-away damp patch in the eaves cupboard above. I pulled away some damp plasterboard:

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The water is dripping down where the celotex type roof insulation ends, coming from between the felt and the celotex. Looks isolated to the area where the buckets are.

The wall with the radiator on is below the side of a small dormer housing an en-suite:
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Some pictures of the same side of the dormer with the lead and tiling:
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The green slime is new, presumably caused by an infestation of pigeons that have been living under neighbours solar panels for the last couple of years. The panels have been sealed up with chicken wire now and the pigeons have gone. If you look carefully at the 2nd and 3rd dormer pic you can see that lots of pieces/tags of lead have been lifted up on the lead adjacent to each row of tiles each - never noticed this before. Could this have been done by the pigeons and is it likely to have caused a leak? Should i fold them up/down?

Any comments on how to investigate / fix this leak much appreciated!

Well on the last picture the tiles are not lined up, which would suggest
not enough overlap.
how many tiles between the skylight and the dormer?

Get out there and move some tiles.

Thanks for your comments. There's two tiles between the velux and dormer.

In the daylight I could see an obvious gap between the rows of tiles nearest the velux.

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I pushed the tiles back up until it was in line, and I also pushed the adjacent one and the row above moved up a couple of cm too. They were all easy to move - shoud;n't they be fixed!?


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Thing is it still started dripping when the rain started again.

Any thought on further investigations?

Well I would lift a tile out as high up as I could safely reach and if it was dry under there then move down a tile at a time until I saw were the water was coming from.

Ok looking at your last picture again there is a difference in tile exposure
meaning they may not all have the correct overlap.
measure the bottom of a tile to the bottom of the next tile and you will see the bottom tile on the last picture is bigger and may not have sufficient coverage.

Thanks - I think the difference in exposure might be where I pushed the tile back up to be in line with the others. The rows of tiles are ~34cm apart.

I've been put there with a bucket of water trying to find the leak and have isolated it to the tile with the notch or perhaps the one above:

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the picture perspective is looking back at the bottom corner of the velux.

There was quite a lot of grime build-up under there which i scraped out - the felt/grime looked damp.

Any thoughts on whether this smallish notch could cause the leak?

There are more photos in the album