Ceiling Joist Size And Spacing For Attic Storage

Uninhabitable attics without storage are those where the clear height between joists and rafters is less than 42 inches.

Ceiling joist size and spacing for attic storage.

I d like to double my ceiling joists to make my attic space easier to work in for electrical plumbing and for lightweight storage. For example the highlighted cell below shows that a 2 x 6 southern yellow pine joist with a grade of 2 and spaced 24 apart can have a maximum span of 10 feet 0 inches 10 0 if you are designing your structure to support a plaster ceiling. 2x4 s actual size spaced 16 on center running the width of the building uninterrupted with the ends resting on top of the wall top plate. The dimensions of the joist depend on the span as well as the load it s intended to bear.

In attics built purely for storage purposes you may find 2x6 ceiling joists or in some cases even 2x4 joists. Ceiling joist spans for common lumber species uninhabitable attics with limited storage live load 20 psf l δ 240 check sources for availability of lumber in lengths greater than 20 feet. The previous homeowner may have simply covered the joists with plywood to use the space for storage. Variations in ceiling construction nonparallel ceiling joist designs require additional support construction in the ceiling.

While this is not the optimal setup it is acceptable to have ceiling joists covered with plywood or osb to use for light attic storage of dead loads. Joist spacing of 24 inches is allowed for spans between 16 to 20 feet using 2 inch by 10 inch lumber of these three grades. 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. 1 inch 25 4 mm 1 foot 304 8 mm 1 pound per square foot 0 0479kpa.

This ceiling joist span table is based on the 2012 irc for uninhabitable attics with limited storage. Building code trainer 2020 therefore if you have an attic space according to this scenario the ceiling joists can be designed for a live load of 10 pounds per square foot psf by using table r802 4 1. It covers 2 common lumber species and sizes at 20 pounds per square foot load. From the table the minimum is 50x97mm which is approximately 2x4 in but it doesn t give any indication of the load that that will bear.

2 x 12 s are not listed because you can span pretty much whatever you want. Although 2 x 4 s are included in the official table they are not listed because it is never advised to use them.