If trusses are being used, the trust layout will be provided from the truss manufacturer. The bottom chord of the truss will be the ceiling joist. Trusses will be laid out and installed as provided by the truss manufacturer. If trusses are not being used, regular 2x6 lumber or larger will be used for ceiling joists depending on the structure. Regular ceiling joists layout is 16 inch on center. However, 24 inch on center can be used but will require 5/8 sheet rock on the ceiling. Once all the ceiling joists are laid out and installed, it will be necessary to install deadwood and blocking where needed in order to secure sheet rock. If Ceiling joists are butted together on top of a wall, it is normally good practice to block the joint. The other alternative would be to lap the ceiling joists at least 6 inches. When trusses are used, the manufacture will provide a specific detail for bracing the bottom cords of the ceiling joist. When regular framing lumber is used for ceiling joists, the ceiling joists will require a strong back nailed across the top. The strong back is run perpendicular and normally in the center of a room’s ceiling joists. The strong back is made up of a 2x4 nailed flat on top of the ceiling joists with 2x6 nailed vertically to the side of the 2x4. The end of the ceiling joist along the exterior walls will require the top corner to be cut off. This cut is the same angle as the pitch of the roof. This prevents the end of the ceiling joists from sticking up above the roof. Once all the ceiling joist are nailed and secure, the rafters are ready to be laid out and installed.