I want to build a home with a loft with a 12/12 pitch roof on it, but am unsure of the roof-ceiling detail. It is about 30 ft. wide by 60 ft. long with 12-ft. 2x6 stud walls. I also want to maximize the headroom upstairs and put a flat ceiling across the entire length of the room. What material do I need to use for the rafters?
There are several methods that can be used to frame the roof you have described. Conventional rafters could be used depending on the room size and available bearing locations. It is important to verify the actual bearing walls. Another option is wood I-joist rafters, which can typically span further than conventional rafters. Or, you could use pre-manufactured trusses. This may be your best option if you do not have actual bearing walls beneath the loft, or if you have limited bearing walls beneath the loft. The wood trusses can be designed to clear span the 30-ft. width and you could expect to get a room width of about half of that depending on the size of bottom chord you use. A truss manufacturer can help you with this design. A good source for finding truss manufacturers in your area is the Wood Truss Council of America.