Our gable-roofed block garage has a partial loft that we use for storage. I would like to finish the other half to expand useable attic/loft storage. There are 2x8-18 at 16” on center which span the space and rest on 10x10s at the top of the block walls and nailed to the rafters. Half is done every 16” and has a floor. The other half only has a joist every 4 feet and does not have a floor but those joists do have 2x4s nailed to them and up to the centerboard of the gable roof. There are ties horizontally between them in the center of the span for framing on the garage door track and opener. There are only 6 rafters without corresponding joists.
I am at a loss for finding 2x8-18 or 2x8-20 locally and do not have a vehicle that would allow me to travel a long distance and bring something so long home. I wonder if I can use 2x8-10 instead and Simpson tie them to the cross members that go in between the joists (that are also ties to the roof centerboard) instead of spanning the whole distance? The brace from the roof comes down every 4 feet. I need this secure enough to put 3/4” OSB as subfloor and store bins of off-season decorations, car roof storage box, and of course us walking up there to fetch things occasionally. Thoughts?