Dihedral Angle Geometry for Hipped Roofs

This short video shows the simple stages of drawing the plan of a roof, then developing the front elevation above to find the dihedral angle.
Once the front elevation is achieved, the true base length of hip is established and used to find the true hip length; a suitable perpendicular point from top of hip is then used as a height. This is finally used in combination with the true base length of hip again to give the final triangle and therefore discover the dihedral angle of the roof drawn (this example is 35 degree pitch).
Draw the plan at any size - this is all about angles - the protractor is the only set measurement used (for the pitch of roof).
Please leave a comment or like if you like 😊.

[@emilyandisobel]

Hi Martin. Thanks for the feedback, much appreciated. Where in the world are you? I’m in the UK and we use a variety of methods for roofing calcs. This video was posted for my college students. I checked out your method, and it came in at 64 degrees for a 35 pitch roof. The geometry comes in at 66 degrees. The true hip length and rise is the same as the plumb cut angle so a great site method👍🏻

[@BillyMustang101]

I haven't seen this geometric version done before, cheers for upload. I find the easiest way is on my framing square, true length hip and rise set out on square.

[@rossaodonovan895]

Nice its been a while since i tech drew a dihedral on a hip, i think you pulled the true length of the hip out there first, geometry is facinating but speed used to be of the essence on site so i was taught to just run the surface planer down and call it a day,id love to see some purlin geometry if you have time, it always confused me