I am looking to upgrade the celing joists in my garage for a room conversion.
Currently have 2x4, 48” OC spanning the entire 22’ length of the garage, supported midway with a perpendicular 2x6 on top.
I need to support ceiling drywall and light storage on top.
I am thinking of replacing with 22’ 2x8s, 24” OC (to match up with the 24” OC rafters.) A friend mentioned that I might have trouble getting 2x8’s that long and might want to tie shorter pieces of lumber together to create this span. I am not sure how to do this properly and ensure that these beams still have enough tensile strength for the roof load. Are 22' 2x8s difficult to get?
2x12 can only span 18' with no center support on 16" centers.
You can use 2x8's up to about a 12' span. Use a beam in the middle of the 22' span under the 2x8s'. But I have never seen floor joist anything but 16" centers. This all depends on how your roof is supported though. You will need to actually calculate loads.
As John said sawn lumber won't work. You could build a floor for storage only with I - joists and plywood deck. If headroom, build it below the roof/wall connection, depends on garage door opener hardware.
Here is info, notice the on center chart below for different spacing (cheaper):