To build a roof over an existing deck may require a building permit in your area. Check your local laws to see if you will need the permit first. After you have a permit you will need to start by putting in supports. After you have your supports in place you will then build your platform for your roof. You will need to then lay the plywood down and nail it to your platform. After this has been
. completed you will start the roofing side of it. After you have completed the roofing you will sit back and relax and enjoy your new roof.