I am building a timberframe with principal rafters. The purlins are 4X8. My questions is can I use simple dovetails at the rafter or must I use a shouldered dovetail?

Thank you,

Allen

Dear Allen:
If you get Steve Chappell’s book “A Timber Framer’s Workshop” you’ll see a section on purlins and dovetails as well as a section on how to determine shrinkage in advance. Possibly these will answer some of your questions.
He states on page 53 that: “shoulder dovetails are used when the members being joined are subjected to an extremely heavy or concentrated load.” Is this your case?
Good luck, Jim.