Advice on leak in tiled roof

My job for the weekend was to remove the polystyrene tiles off the ceiling of one of my upstairs rooms. As soon as I slipped a putty knife behind one, the lath and plaster crumbled and disintegrated:


Removing the weakened plaster shows the laths have rotted away and the bits that are left are wet and full of woodworm:



Must have been leaking for a while! The diagonal piece of wood behind the laths in the pic above appears to be the valley board. Took a pic of the lead valley from street level:



And then another from a precarious position on the top of my ladder with my camera held up above the level of the gutter looking up the valley:


I can see a tile in the valley but when I got into the attic I couldn't see any obvious holes. I think the water is coming in somewhere higher up the valley and then running down the underside of the valley board.

I'm assuming this can't be repaired from inside, so I can't do it myself and will need a roofer.

Is the most likely cause of the leak the fallen tile or something else? Roughly how much is a fair price for a roofer to repair the leak? (I'm in North Wales)

Many thanks.

 

I think the tiles out from the top course under the ridge.
The problem here is an old problem , The lead in the valley has failed and has been patched up in the past.
It needs stripping out and replacing.

Scaffold is required

 

just sayin butdont balance on ladders mate - your not in the circus.

cut back all damaged plaser an plaster lath - chech for any signs of rottin wood.

i cant see the valley saddle but if one valley is work worn the valley on the other side will probly be in the same state.

if you change any valley go for a dry valley trough with a suitable upstand.
to change lead to grp youl have to well strip back on either side.
if the valley boards are rotted change them.

any small off-cut tiles should be clipped - in fact best to clip all valley tiles.
replace any wonky or missin tiles as the work goes.

dont let anyone work on that aged plain tile roof without usin roof ladders
an at least a tied-in tower.

 

Had the first contractor round to look at it, he reckons the lead valley should be replaced with new lead, the valley boards are probably saveable cos it's been caught early enough and he'll work off a scaffold tower. Still waiting on a price.

 

Correct.

 

this can be very costly, I replaced 2 valleys recently to the cost of £3k

 

I've finally had a quote back and he recommends doing both sides (he reasons if one lead valley has failed, and they're a hundred years old it won't be long before the valley on the other side goes too) for about £2k inc. scaffolding. Even that is double what I was expecting. Wish I could get up there myself safely so I could see what the actual problem was!

 

plus vat or inclusive? if it includes then its good taking into account scaffold, a couple hundred quids worth of lead , labour dumping debris.etc

 

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