Broken garage joists
my garage was the same way. same size too. there were only maybe 3 or 4 rafter ties in my garage. all but one was busted and patched with lumber of all different sizes. they were also only 2x4s to begin, not meant for storage. i went with 20' 2x6 joist 16" on center with 1/2" plywood. i know it is not the propper size for any kind of load for a 20' span, but i now have a safer place to put things like holiday decorations and some spare car parts from my hotords. when i go up there, its kind of spongey, but as i said its way better than before. my main reason for doing this was to add more lights, insulation, and have a cieling to keep heat from my woodstove in the work area instead of up in the roof. i didnt want to spend a boat load of cash doing this, and im thinking i can just add some hangers to really stiffen things up.