Frame your new roof.
How to connect a new roof to an existing roof.
After that to make it flush with the roof of the existing house cut the two outer rafters.
To tie into the side of an existing roof put a new roof truss on the walls of the addition brace it upright then snap chalklines on the shingles to mark the center line of the new roof valleys where old and new roofs will connect.
Up from the valley center.
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.
The ends of the shed rafters.
Cover the column frame with siding brick or any outdoor material that matches the exterior of your home.
You have to do it thoroughly so that the rafters sit flush on it.
Re lay the shingles you removed from the existing roof.
Attach the horizontal beam by using a nail gun.
I use steel valleys.
Shingle the addition roof letting the new shingles fold through the valley center and onto the old roof deck by at least 1 ft.
Figure out where the new roof will be on the old one and cut a line up the old roof shingles about 3 away above from this valley line.
Remove siding from the house where the new roof will attach to expose rafters or other framing of the old roof.
Bed the end of each shingle in a 2 in wide ribbon of roofing cement placed 4 in.
Connect a flat roof to a sloped or pitched roof with a ledger board.
Brace the column frame in place using l brackets and concrete screws.
You ll need to pull any nails within about a foot of the valley line so that you can slide your valley flashing up under the old shingles.
Tying in to an existing gable roof.