Velux & Tiling Advice Needed

[junglejim]

I’m in the process of roofing our cassette roof (osb sandwich) on new timber frame build…. Felted, counter battens and tile battens are in. I haven’t started tiling yet but will be soon (sandtoft rivius).

 

I’m hoping to start fitting velux tomorrow but have a question…

 

The window openings have been pre made in the factory. Windows are in several different positions so setting out tiles to windows is unlikely to work for all and I’ve already set out horizontal battens based on optimum gauge for my roof (310mm)

 

As the window position is fixed I’m wondering if there’s anything I can take into account to ensure sufficient overlap between flashing and tiles at the bottom and top of the window and ensuring sufficient width of tiles either side. 

Or… as I suspect will be the case… when I tile, what should I take into consideration?

All advice and learning gratefully received.

[nod]

Work your tiles to the perimeter of the roof You will drive yourself mad trying to set out to your Velux es 

[junglejim]

@nod thanks for help. Also any tips on putting the vcl flashing up underneath my breather membrane above the window which is beneath the counter battens? Presumably need to cut back the counter battens to accommodate?
Thanks. Appreciate all the tips before I get stuck in.