Help! Too shallow for pitched roof?

KatieS

Hi - having an extension done at the mo and the builder has been moaning And groaning about our roof design for a while- he said it's a really shallow pitch but the roofers been round and he can get it to work. He was going on about a 9 degree pitch- not sure if he was exaggerating though. Our current flat roof is 70cm below our bathroom window. The new vaulted roof which will replace this will be over a 362cm wide kitchen- so highest point at 181cm in . Is the pitch really going to be that bad?

System

If it's been designed then surely you know exactly what it's going to look like and how it's going to be built? 9 degrees is a shallow pitch (technically anything less than 10 counts as a flat roof)
But if it has a span of 3600 and a height of 1800 to the ridge you'd be at 45 degrees, so there's some serious miscommunication going on somewhere here

KatieS

the_r_sole wrote: »

If it's been designed then surely you know exactly what it's going to look like and how it's going to be built? 9 degrees is a shallow pitch (technically anything less than 10 counts as a flat roof)
But if it has a span of 3600 and a height of 1800 to the ridge you'd be at 45 degrees, so there's some serious miscommunication going on somewhere here

The height would be 70cm at its highest, with the pitch roof. Owning out 180cm on either side (a width of 360)

Aylesbury_Duck

KatieS, it's all a bit confusing the way you've explained it. A 70cm drop over 180cm is nothing like 9 degrees but I've probably got the wrong end of the stick. We can do the trigonometry if we have some basic measurements and a clear idea of the design. Is there anything you can post, such as a drawing?

EssexExile

What finish are you having on the roof? Surely that determines the minimum pitch?

KatieS

I can't post links to images as I'm not a regular forumite although I'm aware I'm not explaining myself very well! The width of the extension is 3600mm. It will have a dual pitched roof. From leaning out of my bathroom window I can see the current flat roof is 70 cm below, so I'm assuming the new roof will be limited to a height of 70cm due to a window being in the way. Hope I've explained it better

KatieS

EssexExile wrote: »

What finish are you having on the roof? Surely that determines the minimum pitch?

The pitch is being determined by the bathroom window and whether or not it is in the way!

System

Has anyone drawn this up or given you construction details for the roof and junction?
If the window to your current window is 70 cm, it's likely the ridge of the roof will have to be lower to allow for sufficient flashing into the wall...
As someone else mentioned, what roof finish are you using here as your will be limited with low pitches to what is suitable

EDIT: I drew this today (it was annoying me) - the pitch of the roof at 700 height is ~21 degrees and at 600 (which is more likely) it's ~18.5
to get to 9 degrees the roof would only have a ridge height of 285mm