Often in larger structures and barns you may need to split your rafters in two due to the overall length of the building. To accomplish this and create a strong member you can use a rafter scarf joint; in this case we used an under squinted scarf joint held together with long structural screws. It will need support directly under it or close to it in order to carry the roof loads, and it will resist any twisting in the rafter over the years.
Hello,
it is mentioned that the rafter may need to be in two pieces.
Would this be because of not have a timber long enough, thus two pieces are needed? Or could it be a cost factor as well?
Thank You,
Charles
It could be for either of those two reasons. This joint was used in a barn where the rafters were 28 feet long. With such a long after it was cheaper to divide it up and use a scarf joint than to buy 30 foot long timbers.
Could this joint be suitable for a rafter extension where an extended overhang is desired?
A three foot overhang provides outside storage for various materials on the farmstead.
It can be used for that, keep in mind how much load is on the overhang and move the scarf joint up enough to compensate.
Is it common to use a scarf joint when using two beams to create the tie beam for a truss?
No, tie beam are usually in tension and are single pieces. There are scarf joints out there to resit tension but need to be engineered for the location and loads in the frame.
when installing these, is it lifted in two pieces or one
Either but one-piece is the slickest way.
I am scarfing a 4×10 rafter, from center of ledger(3×12) to center of beam(6×12). Two part question; how long should the scarf be? How far should it go past center of beam?