The original post: /r/diy by /u/rob0225m1a2 on 2024-12-23 00:25:42.

Hello everyone!

I am building a lean-to against an existing shed and not sure how to calculate the cut angles for each side of the ceiling rafter.

I’m using 2 x 6 for the rafter that will be 10 feet long. The high side will be at a height of 20 feet and the low side at a height of 19 feet. The rafter will go flush against a ledger board on the shed and against a rim joist on the low side. See attached image for reference.

I don’t know how to calculate the angles on the ends of the rafter. Appreciate any assistance.

https://preview.redd.it/l1qnsxpnsh8e1.jpg?width=780&format=pjpg&auto=webp&s=18b7fe4f05853d4b329fd452bb32a9fc13d3a0cb