cutting rafter help

[Halfathumb]

I'm making a lean to greenhouse. The highest wall is 97 1/8" high. The outside wall (low eve) is 84" high. Adjusted run is 98". I want my pitch at 2:12 but I can't get the speed square to pivot to 2" on a 2x4 rafter. Giving the height of the 2 walls, what should the pitch be? And if I can keep the 2' pitch, what would be the angle of the plumb cut? 

I bought a construction calculator because the math involved was making my head spin.

Jim

[DieselDennis]

If one wall is 8' high (or close) and the other wall is 7' high, and there's 8' (or close) in between them, then the pitch is going to be 1 1/2:12.

I came up with 7 degrees for the plumb cut (or 83 degrees, depending on what you measure from).

[Halfathumb]

If one wall is 8' high (or close) and the other wall is  7' high, and there's 8' (or close) in between them, then the pitch is going to be 1 1/2:12.  

I came up with 7 degrees for the plumb cut (or 83 degrees, depending on what you measure from).

Thank you sir. I also came up with 1 1/2:12 pitch but rounded up to 2 thinking it would simplify things. 

Jim

[KLaz]

Yeah, your back wall should be 100 5/16" for a 2:12.  Plumb cut is 9.46*

[srv52761]

https://www.blocklayer.com/roof/raftereng.aspx

[kdouglaslee]

https://www.blocklayer.com/roof/raftereng.aspx

I used blocklayer extensively a couple years ago when I built roofs for a pair of buildings, 12x32 and 16x16.  Can't tell you how many times I'd print something out, walk out to my project and get to work.  Both roofs came out great as a result.

[Halfathumb]

I used blocklayer extensively a couple years ago when I built roofs for a pair of buildings, 12x32 and 16x16.  Can't tell you how many times I'd print something out, walk out to my project and get to work.  Both roofs came out great as a result.

The rafters turned out ok for a rookie. I'm sure I would do better if I have to do more. The birds mount was the big pain Thanks

[Stwood_]

 The birds mount mouth was the big pain Thanks

Did you make a pattern, to use for marking all the rafters?

[bgosh]

Actually that is a very good web site for rafter's, it takes a bit to understand just what they are saying, for instance to find out the pitch of a roof they give a dimension of 400 and 1200 which really means 4'' or inches of rise and 12" inches of run which is what we normally think of. But really it is a very good web site. Just wondering why you thought you had trouble with the birds mouth cut, making the cut or understanding it? 

[Halfathumb]

Actually that is a very good web site for rafter's, it takes a bit to understand just what they are saying, for instance to find out the pitch of a roof they give a dimension of 400 and 1200 which really means 4'' or inches of rise and 12" inches of run which is what we normally think of. But really it is a very good web site. Just wondering why you thought you had trouble with the birds mouth cut, making the cut or understanding it? 

I didn't make template for the birds mouth, I certainly wish I would've. I understand it but just got sloppy cutting them. I'll certainly know better if there's a next time.

Thanks everyone.

Jim