Hi all,

Looking for some advice on rafter spacing and joinery options:

I need a long roof overhang (~4') to protect the straw bale walls on the cabin I'm building right now, and what I have in the plans right now wont adequately support the loads. Right now, my design calls for 4x8 Hemlock rafters joined and pegged at the peak, meeting the plate with a birds mouth, and then reduced to 4x4 tails that can extend beyond that. The rafters are spaced 4' o.c., and these 4x4 tails at such a spacing wouldnt be able to support a 50 psf snow load. I already have the rafter stock, so I'm not looking to change the rafter dimensions. So, I'm trying to figure out something that would work.

One option would be to add more rafters and put them at closer spacing. What would be the furthest spacing (fewest rafters) to accommodate a 50 psf snow load on the 4x4 rafter tails?

Another option previously recommended was to "taper them from 4x8 at the plate to 4x4 at the ends as long as the birdsmouth was minimal (perhaps 1½" x 1¼") and the plates were notched for the rafters so that there was as little reduction of strength in the rafter as possible at the plate 'hinge' where all the horizontal shear force would be concentrated." (thanks Robert R.) It seems like that would still allow for 4'o.c. spacing.

Any thoughts? Any other ideas?

Thanks a lot,
Dan