Velux on Sarnafil 15 deg Flashing

26 Mar 2020
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United Kingdom
We have a 15 degree pitched warm roof with Sarnafil.
It has 2 standard GGU MK06 Velux windows.

Or Correct flashing method??

My carpenter has built the kerbs ready, to which the Sarnafil fitters have covered right over the top

I'm tired of going between Velux , merchant and tradespeople as to what flashing is needed.
Note Veluxes not on site BUT are due to arrive next week

Velux say "we don't do a flashing" but will sell you a head/ capping accessory kit (ZWC MK06 0000T)
They sent a very complicated drawing (for only a cold roof though) showing the single ply membrane dressed up to either side of the window
Again everyone I've shown this to, questions "Well how's that going to work?"
A coupe of merchants both say "You need the flashing for slates"

Specific advice or experience with this scenario would be most appreciated !!!!
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If you have built a non standard kerb , then obviously Velux won't have a flashing to fit. They will make one. I this case it should be simple for the single ply installer to weather all round , the only bit that will be tricky is the back gutter upstand and this could be dealt with using any flashing back gutter
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Im obviously trying to avoid going above the 150mm (build regs) upstand height
The 150mm upstand would be a minimum to prevent water splashing off the roof surface getting in.
You would only have to worry about how far it protrudes based on any planning/permitted development requirements that apply eg on a front elevation.
If he doesn't know how its going to work then I suggest you have the wrong person!

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