My wife and I are in the process of finalizing the financing on our current land contract for our house with attached workshop. My interest in this place of course was primarily the shop. It is basically a 50' x 100' concrete and stucco building with post and beam supported roof system. The general shape is just a low sloped gable (about 3/12) building with a "doghouse" section at the middle leaving two shed type roofs running the whole 100'. The problem that I am trying to solve is that the roof is currently covered with roll roofing that has a number of minor leaks and worst of all has some substantial sag in some areas (3-4"). My idea was to double up the 2x8 joists which are 24" on center and obviously under sized. I felt that I could add full length joists to each one to eliminate any further sag. (I don't have any hopes of actually removing the dips. The building has been standing since 1920.) The whole roof is covered on the inside with 1x8 T&G pine boards that I plan to remove so that I can get a good evaluation of the roof deck condition from inside. For roofing I would like to run 1x wood strips along the length of the roof and shim them level as I go to bring the roof surface basically back to level. On top of this I would like to put either a corrugated metal or asphalt panel roof. Any advice would be appreciated. Thank you.