Old Roof New Roof Joined Rafters

Nail oriented strand board osb decking over all the new rafters.

Old roof new roof joined rafters. Cut two rafters with a circular saw to the pitch of the addition roof and nail them across the rafters on the old roof. Installing a new roof over an existing one also called a layover or nailover is often possible although not always the best option. Cover the roof with roofing paper overlapping seams generously then nail on shingles. A properly installed layover roof can look and function as well.

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. 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.

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.