Framing A New Roof Over An Old Roof

Use 1 5 or 1 75 inch roofing nails.

Framing a new roof over an old roof.

You can frame a new roof over the old but it will need to be designed for the span and pitch. To provide a framework for the new trusses nail 2 by 6 inch strips of wood around the perimeter of the 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. Or if you want to raise the roof a bit more install fascia around the roof perimeter attached to the new soffit and nail the new roof deck to crown molding above the fascia.

Closed cell polyurethane foam insulation is sprayed around the new roof frame sealing edges and providing support for the rafters and the ridgeboard. The sheathing must be stripped from the old roof for a couple feet along the bottom to get the new ceiling joists in.