Attic joists for live loads.
2x12 floor joists for attic room above garage.
Standard joist spacing for the installation of attic flooring materials is 16 inches on center oc meaning the distance from the center of one joist to the center of the next joist is 16 inches.
Joist dimensions are only part of the equation.
If you need a storage area above your garage strong ceiling joists are necessary to support the added weight.
But you can still double the capacity of the existing 2x6s in the attic floor so first let s make sure that s enough for your situation.
At geoff and michelle s house supply lines for the second floor bath were tucked above the addition s floor joists and only the room s tub sits over the garage.
Attic joists that are made from 2x8s may be acceptable for building your attic floor but because every room is variable there are no absolutes.
Don t forget the impact on adjacent spaces.
You also need to ensure that the joist spacing is adequate.
My calculations tell me assuming 2 southern yellow pine joists which are common in my area that 2x6s 16 inches on center will span 9 feet 9 inches with allowable deflection being the governing factor.
The rest of the space is situated over the laundry room to tap into existing pipe chases.
First floor live loads have higher requirements than second floor live loads 40 pounds per square foot vs.
An inaccessible attic space on the other hand might have a live load of only 20 psf.