Old Roof New Roof Joined Rafters

They form an upside down v with the point at the top of the addition roof.

Old roof new roof joined rafters.

Nail oriented strand board osb decking over all the new rafters. A properly installed layover roof can look and function as well. You can strip the shingles out of the area that the new roof will cover but to be safe i often leave the old shingles in place and frame over them. Remove shingles and other roofing material where the new roof will join down to the deck board of the old roof.

You ll need to install a valley board or nailer over the old roof shingles to create a solid nailing surface for installing jack rafters see drawing. Install bent metal flashing where the old and new roofs meet and on the peaks and metal drip edges along the eaves. Then set one new truss in place against the old roof and use it to snap chalk lines to mark the location on the old roof for diagonal 2 inch by 6 inch valley boards which will hold jack rafters to tie the roofs together. Cover the roof with roofing paper overlapping seams generously then nail on shingles.

Put siding on the new roof end replacing any removed from the old roof area.