Rise: the height of the roof ridge from the center of the span.Span: the length between the outside supporting walls.Know Your Measurementsīefore you cut anything, you need the span, rise, run, and line length of your roof frame. To build a roof rafter, gather the following materials equipment: Collar ties mainly come into play where codes require improved ridge strength, such as in high-wind climates. Although they run parallel to the rafter ties, they sit towards the upper-third of the rafter to resist separation at the ridge – not the walls. Some applications call for collar ties, often confused for rafter ties. A ridge beam can eliminate the need for rafter ties, which is often paramount for the cathedral ceiling aesthetic. For roofs with less than 3:12 pitch, codes require ridge beams because they reduce the extreme outward forces on the walls. Some framing systems use a ridge beam combined with gable-end posts instead of a ridge board, which provides structural support to the rafters. Rafter ties, which often double as ceiling joists, prevent these horizontal forces from causing the walls to "pancake." Ridge Beam As the rafters sit on top of the wall plates at an angle, they exert horizontal forces on the exterior walls. The rafter tie resists the outward forces imposed on the load-bearing walls. The ridge board serves as a nailing surface for the opposing rafters and provides no structural support. The rafters are the diagonal members that directly support the roof deck. Roof Framing: Key Terms and Definitions Rafters This article provides step-by-step instructions for measuring, cutting, and erecting basic gable roof rafters.Ī singular rafter frame typically includes three components: However, building rafters for basic types of roofs like a gable or shed is relatively straightforward with some geometry and carpentry know-how. The roof framing process can get complicated for the uninitiated when it comes to complex roof shapes like the hip, mansard, and gambrel. Rafters also allow for maximum attic space once the structure is finished. Furthermore, individual framing members weigh less than fully built trusses, which means you need less muscle for the job. Photovoltaic shingles should be installed on roof slopes 2:12 or greater (2015 IRC R905.16.2).Rafters can save you on delivery costs and require minimal space for assembly.Liquid-applied roofing should be installed on roof slopes 0.25:12 or greater (2015 IRC R905.15.1).Sprayed polyurethane foam roofing should be installed on roof slopes 0.25:12 or greater (2015 IRC R905.14.1).Thermoplastic single-play roofing should be installed on roof slopes 0.25:12 or greater (2015 IRC R905.13.1).Thermoset single-ply roofing should be installed on roof slopes 0.25:12 or greater (2015 IRC R905.12.1).Modified bitumen roofing should be installed on roof slopes 0.25:12 or greater (2015 IRC R905.11.1).minimum roof slope of 0.25:12 for standing-seam roof systems.minimum roof slope of 0.5:12 for lapped, nonsoldered-seam metal roofs with lap sealant applied.minimum roof slope of 3:12 for lapped, nonsoldered-seam metal roofs without lap sealant applied.Metal roof panels should be installed on roof slopes according to particular seams (2015 IRC R905.10.2):.Built-up roofs should be installed on roof slopes 0.25:12 or greater (2015 IRC R905.9.1), except for coal-tar built-up roofs that have a minimum roof slope of one-eighth unit vertical in 12 units horizontal (1% slope).Wood shakes should be installed on roof slopes 3:12 or greater (2015 IRC R905.8.2).Wood shingles should be installed on roof slopes 3:12 or greater (2015 IRC R905.7.2).Slate shingles should be installed on roof slopes 4:12 or greater (2015 IRC R905.6.2).Mineral-surfaced roll roofing should be installed on roof slopes 1:12 or greater (2015 IRC R905.4.2). Metal roof shingles should be installed on roof slopes 3:12 or greater (2015 IRC R905.4.2).Clay and concrete roof tiles should be installed on roof slopes 2.5:12 or greater (2015 IRC R905.3.2).Asphalt shingles should be installed on roof slopes 2:12 or greater (2015 IRC R905.2.2).
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