How to Connect a Porch Roof Onto Your Existing Roof

Fasten a sill plate to the house in between the porch's side support beams. The sill plate lets you secure the porch's wall supports to its roof.

Position the rafters over the sill plate in accordance with the pitch of your existing roof. Secure the rafters into the sill plate with screws. The rafters must overhang the roof by at least a foot on both sides, but additional overhang may be necessary depending on the roof's pitch. The overhang protects the porch walls from weather while simultaneously balancing the line of the roof.

Slide joist hangers over the edges of the porch roof where the rafters meet the sill plate. Nail the joist hangers in place. Joist hangers give your new porch roof additional support.

Nail plywood boards over the rafters. Cover the entire porch roof frame with plywood.

Measure the height of the rafter ends and the roof length. Cut the fascia board to size. Nail the fascia board to the rafters around the entire porch roof structure.

Lay drip edge over the edge of the roof and the fascia board. Nail it into place. Overlap each piece of drip edge by 3 inches. Install the drip edge on the sides and front of the new porch roof.

Install the surface roofing material. For a seamless appearance, use the same roofing material for your porch roof as you used for your home roof. For example, if your home has a clay tile roof, you should also install clay tile on your porch's roof.