Adding a roof to your porch provides you, and your porch, with much needed protection from the sun, wind, rain, snow and ice. However, you must ensure the new porch roof matches with your existing roof seamlessly to enjoy these benefits. If you have basic carpentry skills, and understand basic framing techniques, you can attach a porch roof to a house.
Check your local building codes before beginning construction. Acquire any necessary building permits before starting work. Your local building codes office may require you to submit your plans for approval, so it's a good idea to draw up your plans before you begin the job.
Build support columns to help support the weight of your porch roof. If you have a square porch, you need support columns at the two corners farthest from the house. Using two-inch by four-inch studs, build a frame for columns that stand from the porch floor to the soon-to-be-built roof. Brace the column frame in place using L-brackets and concrete screws. Cover the column frame with siding, brick or any outdoor material that matches the exterior of your home.
Attach a sill plate to the house between the two side supports of the porch. The sill plate, or piece of wood that secures the supports to the roof, should sit flush to the top edges of the roof support columns.
Position the rafters on top of the sill plate. Joist hangers can help you mount each rafter to the house. Use screws to secure the rafter to the sill plate. The positioning of your rafters will depend on the pitch of the porch roof. The porch roof may match the pitch of your home, or have a more shallow roof pitch. If you decide on a shallow pitch porch roof, use 2-by-6-foot rafters.
Frame your porch roof by continually adding rafters, until it extends one foot past your porch walls or support columns. A fascia board, which is a roofing material that helps compensate when there are inevitable inconsistencies in rafter length, will mount on the front and on the sides of your porch roof frame. Hold the fascia board against the rafters, and then hammer it in place with galvanized finish nails.
Cover rafters with thin sheets of plywood. Hammer the plywood into the rafters until it's secure.
Pick roofing materials that match your existing roof. As long as you use a roofing design that matches your existing roof, you can use the same materials. However, if you build a porch roof with a peak larger than your existing roof, check to make sure the that material can stand up to the pitch of your porch roof. Different roofing material functions best when installed at a certain pitch, so you should check with the manufacturer to make sure the pitch of your roof matches the manufacturer recommendations.
Add your roofing materials to the porch roof starting at the house and working your way out to the edge of the porch. It may be necessary to pull some of the shingles off the house to create a seamless pattern onto the porch roof.