How to Connect a Porch Roof

Check building regulations for permits required to add a porch roof. Locate framing members on the wall strong enough to support the weight of the porch roof, such as rim joists between floors on a two-story house, double wall plates or vertical wall studs on a one-story house. Find these by looking at the inside of the wall in an attic. Mark the locations by driving 16d framing nails with a hammer through the wall from inside.

Remove the house siding with a pry bar in an area slightly wider than the porch roof and high enough to provide a slope to the columns that support the outer edge of the porch roof. Make a slope of at least 2 inches per foot, more in areas with heavy winter snows, so the roof will drain. Mark that height on the wall on each side of the porch using a tape measure and marker, and snap a level chalk line between the points for the top of a ledger board.

Nail a 2-by-6-inch or 2-by-8-inch board, depending on the size of the porch roof, along the ledger line with framing nails and a hammer. Make sure it is perfectly horizontal using a level. Make it at least 1 1/2 inches wider than the porch roof on both sides or the same width as the outside supports. Mark the connecting points of the joists or studs along the length of the ledger.

Drill holes with a power drill and 3/8-inch bit through the ledger into the house wall framing. Drive 1/2-inch lag bolts long enough to penetrate the ledger and wall sheathing at least 1 1/2-inches into the wall frame. Lag bolts have pointed screw ends with bolt heads and are driven with a ratchet wrench. Put washers on the bolts on both sides of the ledger, to allow for drainage.

Secure outer beams between the ledger and the tops of the outside posts or other supports. Use metal joist hangers on the ledger for a strong connection. Nail the base of the hanger to the ledger, set the beam or joist into the support slot on the hanger and nail it in place through the holes in the hanger sides. Install rafters, roof decking and roofing once the porch roof frame is connected firmly. Place metal flashing up the wall and down the porch roof before installing roofing and replacing wall siding.

Attach a gable or angled roof using a similar technique. Install a base ledger, but add gable ledgers from that board to a gable peak to match the angle or slope of the gable roof. Fasten the gable ledgers with lag bolts to wall studs, placing a bolt in every stud from the bottom of the slope to the peak.