Rafter Birdsmouth Calculation

[airman89]

I don’t know how I’m messing up this rafter cut but I’m going to lose my mind if I don’t figure it out.

I have a low pitch porch roof with a 2x10 ridge board. Rise is 23”, building width is 166-1/8”, rafters are 2x8, seat cut is 5-7/8”, the heel cut height is where something is off. The rafter is 4-1/2” higher than the ridge… I can’t make up the difference at the heel cut because I will no longer have an overhang… I’m using the rafter calculator too..


https://www.omnicalculator.com/cons...IDOLVS/b16WXEqkKyiLCsixcz0FU5+PdfmEn1Np8xAAA=

 

[PCustoms]

If everything else is OK then I assume your total rise is off...

 

[J-Man22]

Try using the Construction Master Pro calculator. You can either buy the calculator if you'll use it again, or there is an app. I just built a gazebo with a hip roof, never framed a roof before, and that app was extremely helpful. Gives you all the lengths, angles etc based on your building dimensions. There are some good YouTube videos by Training Hands Academy. I watched the one on framing hip roofs which was very informative, and he explains how to use the calculator in that video too. He has other ones on rafter basics, lean-to roofs etc.

 

[cgrutt]

Does porch have a peak as shown in calculator or is it more of a shed style roof, with ridge board attached to building? Building width that calculator uses may be off if its a shed style roof (you may need to multiply actual width by two). Just guessing.

 

[nutjob]

Try this:
https://www.redxapps.com/build/roof Than select rafter, than common.

I just used this for a shed project and found it was about the best for what I needed

Kevin

 

[67carl]

I feel your pain. I had similar issues with bird-mouth cuts on my greenhouse build. It got so much worse when I needed to frame the valley rafters. Holy cow, never again.

 

[airman89]

Try this:
https://www.redxapps.com/build/roof Than select rafter, than common.

I just used this for a shed project and found it was about the best for what I needed

Kevin

This was the one that worked best for me. Still slightly off but I pinpointed it to the OSB spacers in between the beam plies caused the beam width to vary slightly thus throwing off my rafter cuts. Here they are. Hung up and notched for purlins.