Flat roof falls on extension with 2 roof lanterns

[Zoe_ag]

Hi! Totally new here!

 

I'm an architectural assistant, I completed a masters degree in Architectural Technology in August

 

I'm doing a simple GF extension for my parents - They wanted parapet walls, so I've gone for a warm roof - but what's the best way to do the falls? 

They dont want the downpipes on the rear the elevation with the bi-folds looking onto the garden.

 

whether you go from the existing house to the back, or centre outwardto the sides, you hit the lanterns, and I'm thinking you need some kind of box gutter to get it to the outlet with hopper?

 

I've looked at doing sloped valleys to single outlet points on the side walls by cutting tapered insulation at a 45o angle, and that seems to be a good way to avoid pooling around the lanterns - or is this just over complicated? I'm worried builders just won't be bothered to do it like this.

 

thanks, Zoe

 

 

[markc]

Lanterns are always going to obstruct falls in at least one direction. Your idea is great in principal but as you fear the builder is unlikely to follow it to the letter and you probably end up with a flat roof with a lowered outlet.

[Zoe_ag]

10 minutes ago, markc said:

Lanterns are always going to obstruct falls in at least one direction. Your idea is great in principal but as you fear the builder is unlikely to follow it to the letter and you probably end up with a flat roof with a lowered outlet.

What do you mean by lowered outlet?

[markc]

51 minutes ago, Zoe_ag said:

What do you mean by lowered outlet?

Majority of builders/roofers would take the easy route and basically lay a flat roof but then a small area of fall local to the outlet, like a shower tray. Its not a big area of roof so if you work on the premise that some water will pool around the lanterns - with waterproof upstands. Saves a lot of work and expense putting all the falls in.