Attic Floor Joists Size

Joist span tables.

Attic floor joists size. This sample table gives minimum floor joist sizes for joists spaced at 16 inches and 24 inches on center o c for 2 grade lumber with 10 pounds per square foot of dead load and 40 pounds of live load which is typical of normal. If the attic joists are not adequate one way to strengthen the floor for live loads is to sister the old joists. If you need a storage area above your garage strong ceiling joists are necessary to support the added weight. Sistering is the process of adding a new joist next to each existing joist.

Beyond the size of joists the spacing between them should also be taken into consideration. You need 3 4 inch plywood. The overall strength of the flooring joists depends not only on the size of the span but also on the distance between the support. For 2x6s joists you can get away with some relatively light stuff.

Know the difference between your ceiling and floor joists. They are designed to carry only the weight of the drywall or plaster depending on the age of your home. Joists of 2x8s or larger are able to support more weight. Joist spacing and attic use the joist spacing in some attics is 24 inches and 1 2 inch sheets will sag and possibly break when spanning that distance.

Trust me on this one. 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 have an attic over your garage these joists also bear the load of your attic flooring and any materials you store in the attic. Standard joist spacing for the installation of attic flooring materials is 16 inches on center oc.

If the second story windows etc will support he roof it will support the new attic floor. 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 dimensions of the joist depend on the span as well as the load it s intended to bear. I ve found this page of common domestic floor joists sizes.

Please read disclaimer at end of description sorry this is my first video and i do a terrible job explaining but. The wooden joists or beams over your garage help hold your roof in place. Shirlock homes ok. An inaccessible attic space on the other hand might have a live load of only 20 psf.

More times than not the floor structure of an existing attic is actually a ceiling joist. If you find that you d like to store more weight consider adding an osb for attic floor. Here s how to make undersized and o.