Old Roof New Roof Joined Rafters

A properly installed layover roof can look and function as well.

Old roof new roof joined rafters.

Cover the roof with roofing paper overlapping seams generously then nail on shingles. A new level 2 6 ridgeboard and rafters then are assembled over the old roof and are attached to the existing structure with nails and lag screws driven into the underlying wall top plates. 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. They form an upside down v with the point at the top of the addition roof.

Nail oriented strand board osb decking over all the new rafters. 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. Installing a new roof over an existing one also called a layover or nailover is often possible although not always the best option. 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.

Cut two rafters with a circular saw to the pitch of the addition roof and nail them across the rafters on the old roof.