- Q. Framers in our area
typically splice long hip and valley rafters with the scarf
joint shown in the illustration. Is this adequate to support
the roof load?
A.Robert Randall responds: No, the scarf
joint you show is not adequate to support typical roof
loads on a hip or valley rafter. These members must be able to
function as bending beams carrying substantial vertical
Hip and valley rafters should never be compromised by such a
weak splice. If splicing is required, secure a sister that runs
at least four or five feet on either side of the joint. This
splice should be capable of developing the full bending
strength of a continuous member. Spike the overlapping piece
together with plenty of well-placed nails, or better yet, with
carriage bolts, as shown.
An even better alternative would be to use engineered lumber
(such as Microlam LVL), which is available in the required
lengths. Although this material will cost more, it will offset,
at least in part, the labor cost of making a splice. And the
end result will be superior.
Robert Randall, P.E., is a structural engineer in Mohegan