Old Roof New Roof Joined Rafters

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.

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

A properly installed layover roof can look and function as well. Remove shingles and other roofing material where the new roof will join down to the deck board of the old roof. Nail oriented strand board osb decking over all the new rafters. Install bent metal flashing where the old and new roofs meet and on the peaks and metal drip edges along the eaves.

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.