atticattic-conversionframing
The attic above my garage has several of these horizontal support beams across the ceiling joists, I assume to keep them from bowing. I’d like to put down plywood across the whole floor without these because they’re a tripping hazard.
Are these supporting pieces necessary? Can they be replaced by plywood and still keep the joists from bowing?
Just to clarify, I’m not referring to the beams holding up the roof, just the non-load-bearing ones.
Yes. Very possible. It has to be engineered though. We have plans to do just this. The drawings and engineering cost around $1000. I wouldn't try it unless an engineer has looked at it, drawn a plan and signed off on it.
For us we are going over a 3 car garage and the roof pitch is 12-12. So a lot of space there. The plan is to remove the drywall ceiling in the garage and install 24" engineered joists (2x4's). We lose a little head room in the garage and the space above, but not much.
Then once the floor system is in place it's much easier to move around. 2x6 rafters installed with collar ties at about 8.5 feet, and plywood gussets with engineered nailing patterns at the peaks. Then cut away the trusses. Doing it for about $80 a foot, and it will add about 500 square feet.
I think they're there for stabilizing the brown beams/joists. Typically, a loft is unused space with no floor. Between the joists, there is insulation supported by drywall or other material depending on the age of the house (as in pic 2 and 3).
Typically one would put in blocking between joists to stop horizontal flexing and torsion.
Since an attic is usually unused space, I think someone took a short cut and just screwed the 2x4s to the tops of the joist. (Significant labour savings!). Your flooring probably makes it unnecessary from a flexing point of view, but you still have a torsion problem (especially since you're now loading the joists).
When you go to make improvements, block the joists properly, but I wouldn't worry in the short term.
Best Answer
They seem to be 2x8, spanded out to the max,with strong backs added to help the frame.Witch is fine for a ceiling joist,to only handle ceiling load. Now you take the strong backs off weaken ceiling joist frame. Want to add plywood more weight.and you make them floor joist,if any load or a room is added due to span you may be under sized. If 2x10 and short span maybe fine .2x12 16 inches on center ,I would say your fine. After finding out you have a 20 foot span .2x12 24 on center changes things they are spanded out to the max.and strong backs added to help them . Adding plywood and taking out strong back not a good idea. Not a good spot to store stuff.