Need help figuring roof rafter angles

[drumz]

I have a large deck that sticks out into our yard so the deck sits up on a slope. We decided to raise chickens so I built a coop underneath because it is 8 feet at the tallest end back to about 4 feet with the whole inner area about 8x8. So you can walk in there and there's plenty of room for nesting boxes and perches. Well I had constructed a funky gutter system between the joists but it just wasn't waterproof enough so I decided to roof the top of the coop - the old deck floor. The problem is it is at an 80 degree angle from the front
Does anyone know what the angles should be for the roof rafters at the plumb cut and the birdsmouth cut or how I figure them out? I only have to do 5 for each side but short of temporarily rigging a ridge board and then manually laying them out I am not sure how to start.
Thanks very much for you assistance!

[chandler]

Not totally sure what your plans are. Are you installing a roof system under the deck, using the deck as a roof, roofing the deck, or what? Not sure as to what the 80 degrees is, as the drawing is just a parallelogram.
Measuring for rafters can be done with a torpedo level and an adjustable bevel guide. Either that or a tool like this:

[drooplug]

Framing square. That's how I learned how to lay out rafters. To do it this way you need to know how many inches the roof drops vertically per 12" of horizontal run. I believe the minimum slope for a 3 tab shingle is 3" per 12" of run. That is refered to as a 3 on 12 slope. You would then take you framing square and using the outside edge of the square, line up one of the legs at 3 and the other at 12. That's your angle.

[drumz]

Thanks, I have different angles so I think I'm going to put the ridge board up and then lay them out with my bevel square and then use the framing square. Thanks for the framing square tip that will be a big help.

[chandler]

Oh, I have chickens and you won't like them under your deck, believe me. The ammonia will eventually run you and your visitors back inside.

[drumz]

Yup, but they are way out in my yard and downhill and the wind usually blows towards it and not from it from where we are Plus, the way I built the coop we can take a hose and spray it out; the floor is made of that plastic grid like fencing that slides out for hosing down too and doing it every 2 or 3 weeks keeps it pretty manageable.

[agent91]

You can't just come up with numbers and expect them to work, you need to know the rise and run of the roof, you have the run there, 8 ft, divided by 2= 4 ft run, with a ? rise, On the framing square, common rafters run per foot. Is a denominator to multiply this run with to get the angle for the rise. You can lay this out on the deck, using the deck for the run and the rise is anything you want. Draw the lines on the deck, cut each piece, even make trusses, gang nail them together.
We did a house once, monster beams and rafters, like 22 inch by 12 ridge beam, and 16 by 6 inch rafters, we spent days cutting these things, nobody knew what they were doing, and I was the new kid on the job, they wouldn't listen to me, but I told them it wouldn't work. The big day came, two cranes,at $75 an hour, one holding the ridge in place while the other one tried to fit the rafter to it, and bolt it together, whoa, way off . Took it down, recut every rafter, got it back up there, nobody ever checked the run , let alone the rise. They were just guessing, 6/12. Yeah, 6/12 is fine, but you still need length common rafters per foot run. Hope this helps.

[angielily18]

You just have to set it in different angles to make it better and the wind could be passing to it. The rafter angles is very important, and it is not easy to plan.