Joe doesn't know what headlap is and is the Forum village idiot btw.
That said, it'd be worth investigating the leak further before condemning the lot.
Xenon";p="2387974 said:
Zoomed in, and i can't see any interlock
The interlock is on the spare slates at the end of the roof.
They look to me a bit like a Sandtoft Penine slate or similar as I can see no interlock so they are double lap slates laid with a single lap. The felt must be keeping the water out to the rest of the roof so the felt may have dropped at the top edge or is getting through a side lap of there is any.
Seems to be getting more and more common that a builder is doing their own roofing at the moment rather than paying for a specialist. After the early 90's recession we ended up with a fair amount of work putting things right when the same situation occurred
#edit#
Just seen your comment about flashing being below where the piccy is taken from. Is it a side abutment to a wall? If that's the case it could be a soaker / secret gutter problem
Oh dear, what a disaster. Rip it off and start again with someone who knows what they are doing.
And you shouldn't use those things at 17.5 degrees even if you had 4" lap or more, they're not suitable at such a pitch.
1. Rip it off and start again
2. Change the roofer.
3. Change the tile or the pitch.
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