Rafter Scarf Joint

Rafter Scarf Joint

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.  

Rafter Scarf JointRafter Scarf JointRafter Scarf Joint

9 thoughts on “Rafter Scarf Joint”

  1. 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

    1. 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.

  2. 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.

    1. 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.

    1. 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.

  3. 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?

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