Position the gable porch truss flat against the porch ends wall top plate and start working backward toward the home. Make sure to set the trusts by bracing them together.
Secure the truss closest to the house first and fastened with nails on both sides extend a cord or string line on the level from the peak to the roof line highest point or peak. Begin nailing the ridge board to the gable roof.
Set the valley rafter starting with the ridge board at the roof's downward point to the porch truss. Fasten the jack rafters that are vertical to the ridge board going down to the valley rafter. Spacing will be contingent upon the local building codes and requirements that will vary depending on where you live.
Continue with conventional techniques for completing a roof by installing the sheathing. Identify the width of sheathing used on your existing home roof and duplicate the installation on the porch.
Measure all of the sheathing before installing them onto the gable porch roof. Place the sheet end at the center points of the roof truss rafters and the adjacent sheets will share the same nailing area or surface.
Begin rolling out the felt starting from left to right. Start the first run from the bottom and overlie each run between five to six inches. Make sure to add metal flashing on the roofs valley and along the lowest ends or edges. Utilizing this method will help to prevent water damage or leakage. .
Install the shingles that match the existing roof shingles. Like the felt installation begin at the bottom and work up. Paint wood or siding to complement your home. A staple gun or nail gun is the recommended tool for fastening the shingles onto the roof. If you live in a location where high winds are an issue you may want to use a nail gun.