Things You'll Need
Power drill and bit
Adding a roof for a porch, patio or deck can be a complex undertaking. It requires building roof framing, figuring slope angles and designing a roof, from a simple single-slope shed style to a more complicated gable version. The complexity of the job will vary with the size of roof, from a simple entryway covering to one over a large screened-in area. A common element in adding porch roofs is fastening one end to the house, either to a wall or to a roof. That usually is done with a header or ledger board, secured to the house.
Locate a position for a header or ledger board. Determine how high it must be to provide an adequate slope to the roof. Make it the full width of the porch or slightly wider, depending on your porch design. Find the wall studs or roof trusses that will have to support the ledger. Look in an attic, if the location is on a roof slope, or check the interior walls to find studs. Use a stud finder to help locate studs.
Remove the shingles or siding in the area identified for the header board. Take off enough covering to expose the wall sheathing or decking and show the nails used to fasten it to studs or trusses. Leave the decking or sheathing in place. Measure with a tape measure from the porch floor to the height required on both sides of the porch and snap a level chalk line between those points to mark the bottom of the header.
Buy lag bolts long enough to go through the header board and into the studs or trusses by at least 1 1/2 inches -- lag bolts have a bolt head and a pointed screw end. Mark all the stud or truss locations and mark identical spots on the header board. Pre-drill holes in the header and studs or trusses with a power drill and a bit slightly smaller than the lag bolts to be used for the header. Put one lag bolt in each stud or truss.
Set the header board in place; get help to hold it straight along the level line. Drive a lag bolt into one end with a ratchet wrench to secure that end. Move to the other end and put a bolt there. Secure those bolts and install bolts at every other location.
Put metal flashing behind the header, one side up the wall or roof, the other side over the top of the header, to seal it from water.