Tips for tying in a porch roof addition include covering the plywood of the frame with roofing felt before laying shingles as well as erecting the trusses, tie-in rafters and overhang before sheathing and shingling. Most porches and decks lack strong enough footings to support a new porch roof. Installing additional supports at the center and edge of a new installation may be necessary to distribute truss and rafter loads.
The process of installing a porch roof addition involves erecting support posts before constructing the frame. Dig holes that are 18 inches deep at the corners of the porch, and place support posts in the holes before pouring concrete and allowing it to set. Construct and assemble the roofing frame using cross-bar supports to provide additional stability.
Have an assistant position and stabilize the frame and then secure the completed frame to the top of the support posts using heavy-duty bolts. Measure and cut the roof to ensure an overhang of at least 2 inches on either side before installing it above the frame. Cover all exposed plywood with roofing felt, and secure the felt using roofing tacks before sheathing the roof and installing shingles that match the existing installation.