Orangery Flat Roof Upstand Problem.

[Woody3]

We are just about to start phase 2 of our extension works, which involves constructing an Orangery. We are currently at this stage. No builders are on site.



These are the plans:







The two windows that are above one another (just under the scaffolding) are causing us a bit of bother, as we are unable to touch the stone head/sills/transoms/jambs (Listed Property).

Problem number 1: The joists. Is there any reason why I can't run the joists from the left (the fireplace wall) to the right?

Problem number 2 (the main problem): The upstand (see below photo). Roof construction will be along the lines of 220mm metal web joists (be nice if I can engineer these slimmer), 125mm ply insulation (the thinnest I can get away with I'm lead to believe) + roof covering, assuming EDPM at the moment. There will be a minimum of an 150mm upstand around the perimeter. As I'm not allowed to touch the stone window surrounds, how do I ensure a watertight finish around the window area?

Please note, the actual timber windows can be removed and blocked up with stonework.



Any thoughts?

[Woody3]

Thanks for the replies chaps.

Roofer - the problem is that I'm not allowed to cut the stone window jambs, thus not being able to tuck the membrane in on either side of the window. The jambs are 100mm wide. Does that make sense?

[Woody3]

Again thanks for all of the replies. I'm hoping to stick to metal web joists, but if changing to traditional joists saves me some head height, then it could be a consideration.

Having said that and just seeing the last reply, do termination bars omit the need to chase? Never seen/heard of them before, well not knowingly anyway...

[Woody3]

Thank you all. I can now get my builders to price the works up now we know how high we are building!

Cheers!