Rafter Calculations for Different Plate Levels

How to find the rafter lengths for roofs that have different wall plate levels.

[@bravo3541]

Good one Michael. I almost figured it out (pausing video) but didn't add full span step. Keep 'em coming lad.

[@michaeldownes516]

Thanks, will do!

[@T.E.P.]

hey ya! good animation thanks for making this

[@michaeldownes516]

I'm glad you like it

[@benshaw8139]

If I was cutting a rafter for a 35 degree pitch my plum cut would be 35 how did it become 55 in your example ?

[@michaeldownes516]

Hi Ben, if the pitch of the roof is 35 degrees..the plumb cut will always be 90 minus the pitch. In other words the Plumb Cut plus Seat Cut (Pitch) should = 90 degrees. If you visualise another example...take a 30/60 degree set square...if the 30 degree end of the set square represents the pitch (seat cut)of the roof...then the other end represents the plumb cut (60 degrees).

[@benshaw8139]

I 100% get what your talking about it all adds up to 90 etc but it literally makes no sense to me as someone who has done a lot of traditional cut roofs if the pitch of the roof is 30 degrees then I would cut 30 on my chop saw for the plumb cut but if I was to do as you said on the video I should in fact be cutting 60 on the chop saw to achieve a 30 degree pitch regardless I like your videos sorry if its like talking to a brick wall

[@michaeldownes516]

@@benshaw8139 ..so when you swing your chop saw to 30 degrees and chop...then the angle left between this cut and back of rafter (Saw Fence) will be 60 degrees (Plumb Cut Angle).

[@benshaw8139]

@@michaeldownes516 I suppose when working it out on paper that’s how you’d have to say it because your showing us the degree and the angle in the same example witch now I know that’s what you mean and why you said it that way but I can almost say with Surtenty that if you said to someone the plumb cut of the roof is 60 degrees and walked away and came back you’d find a roof set at a 60 degrees pitch