2x12 Floor Joists For Attic Room Above Garage

Attic joists for live loads.

2x12 floor joists for attic room above garage.

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. If you need a storage area above your garage strong ceiling joists are necessary to support the added weight. 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. A room used solely for sleeping might need to carry only 30 psf whereas a garage floor over a basement would need 50 psf or higher.

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. The rest of the space is situated over the laundry room to tap into existing pipe chases. 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. If you have an attic over your garage these joists also bear the load of your attic flooring and any materials you store in the attic.

You also need to ensure that the joist spacing is adequate. Don t forget the impact on adjacent spaces. The wooden joists or beams over your garage help hold your roof in place. Joist dimensions are only part of the equation.