Calling All Roof Framers ( Help!?)

djmesh

First off im from the uk, so we dont do a lot of roof framing its mainly trusses. anyways iv attached a sketch of a small roof below, its a regular hipped roof, the rafters on all planes of the roof are to be a 35 Degree pitch.

Normally when framing a hip roof, we will drop the hip, but its important on this occasion that we plane on the backing angle. my question to you guys is how do i find this angle practically when on site? given the above dimensions etc.



Probably sound like a noob

any help would be massively appreciated guys

Joe Carola

Do you use a framing square to figure out your rafter lengths or a Construction Master calculator? That answer will let me know what way to show you.

You said the pitch is 35°. That makes it around a 8-3/8:12 pitch. The backing angle is 23.92746° or 24°. Are you backing this because it's a wide hip or the bottom of the hip is planing in with the bottom of the jack rafters because of a cathedral ceiling and sheetrock?

__________________
Joe Carola

djmesh

I do my framing using a speed square its being backed because the drawing states that it must be as part of regulations, no idea why to be honest. so how do you work it out as 24 degrees then?thanks

Aframe

Using Framing square (in inches sorry)
Common Rise /over Run = ex. 8:12
Common rise /45 degree hip run = 8:17

It will be the same as if you were planing off the top of the rafter, you will or need to raise or lower the seat cut to match the rafter face your lining up with
Speed square gives you common and hip angles on different scales,

Correct me if I have this wrong but, does the drawing matches the dimensions you have?

By the dimensions you give 2500/2600mm you either have to give up a true 45 degree hip or adjust the pitch on one plane of the roof.