flat roof abutting existing pitched roof - felt detail?

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Hi - we're having a flat (1/60) roof built abutting an existing garage dual pitch roof. The 1/60 direction is along the length of the pitched roof.

To my layman's eyes, the existing felt on the pitched roof should be lapped over the waterproof top of the roof, in case of water ingress under the tiles. However, the builder has tucked the felt under the lower deck and insulation - see pic. Surely if there is water getting under the tiles, it will just flow into the interior of the extension?

Am I right, or is there nothing to worry about here?
 

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thanks, yes i was expecting them to do something like this. I had already asked them about it and sent a pic from the NHBC :rolleyes:
 

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Looks like the same as the NHBC diagram. That’s the VCL going under the OSB, the waterproof membrane will go on top surely?
 
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The NHBC diagram is better but could be improve. FWIW:

1. there should be a deck above the insulation.
2. the deck felt runs across the deck and up the slope for ..? It depends on the construction.
3. the roofing felt comes down & overlaps the sloping upstand of deck felt.
4. much of this detailing, eg with the V/B, depends on the construction detailing at the junction, and the type of roof.
5. with roll materials, higher always overlaps lower - just like courses of slate or tile.
 

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