How to Connect a Porch Roof to an Existing Wall

Locate the area on the house wall where the porch roof will connect. Make sure it is high enough to provide a decent slope, at least 2 inches per foot, for the porch roof. Find supports in the house to hold the new roof, rim joists between floors on a two-story house, wall plates or studs on a one-story house. Identify these points by looking in an attic or finding nail points on house siding. Mark them on the house wall.

Remove the siding along the connecting point with a pry bar. Pull the nails and try to preserve the siding for replacement later. Strip the wall down to the sheathing. Use a tape measure to mark the height for the porch roof connection on two ends and snap a level chalk line to mark the top of a ledger board or nailer board for the roof connection.

Nail the ledger, usually a 2-by-6-inch board, in place temporarily with framing nails and a hammer and mark the locations of studs or other supports on the house walls. Drill pilot holes through the ledger and into the house wall supports with a power drill. Use a 3/8-inch bit as a pilot for 1/2-inch lag bolts.

Fasten the ledger to the house wall with 1/2-inch lag bolts, long enough to penetrate the ledger, house sheathing and into the wall supports by at least 1 inch. Use a ratchet wrench to drive in lag bolts, which have a bolt head but pointed screw ends. Nail metal flashing up the side of the house wall and over the top of the ledger board.

Secure the frame of the new porch roof to the ledger with 16d framing nails or with metal brackets fastened to the ledger to support rafters or framing bands of the new roof. Re-install the house siding once the new roof is in place.