The braces shall be spaced not more than 4 feet (1219 mm) on center and the unbraced length of braces shall not exceed 8 feet (2438 mm). Purlins shall be continuous and shall be supported by 2-inch by 4-inch (51 mm by 102 mm) braces installed to bearing walls at a slope not less than 45 degrees (0.79 rad) from the horizontal. Purlins shall be sized not less than the required size of the rafters that they support. Installation of purlins to reduce the span of rafters is permitted as shown in Figure R802.5.1. TABLE R802.4(2) CEILING JOIST SPANS FOR COMMON LUMBER SPECIES (Uninhabitable attics with limited storage, live load = 20 psf, L/Δ = 240) CEILING JOIST SPACING (inches) For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 pound per square foot = 0.0479 kPa. TABLE R802.4(1) CEILING JOIST SPANS FOR COMMON LUMBER SPECIES (Uninhabitable attics without storage, live load = 10 psf, L/Δ = 240) CEILING JOIST SPACING (inches)Ĭheck sources for availability of lumber in lengths greater than 20 feet. For other grades and species and for other loading conditions, refer to the AWC STJR. Spans for ceiling joists shall be in accordance with Tables R802.4(1) and R802.4(2). Collar ties shall be not less than 1 inch by 4 inches (25 mm by 102 mm) (nominal), spaced not more than 4 feet (1219 mm) on center. Collar ties or ridge straps to resist wind uplift shall be connected in the upper third of the atticspace in accordance with Table R602.3(1). Spans for rafters shall be in accordance with Tables R802.5.1(1) through R802.5.1(8). Where ceiling joists or rafter ties are not provided, the ridge formed by these rafters shall be supported by a wall or girder designed in accordance with accepted engineering practice. Rafter ties shall be not less than 2 inches by 4 inches (51 mm by 102 mm) (nominal), installed in accordance with the connection requirements in Table R802.5.1(9), or connections of equivalent capacities shall be provided. Where ceiling joists are not parallel to rafters, rafter ties shall be installed. Where ceiling joists are not connected to the rafters at the top wall plate, joists connected higher in the atticshall be installed as rafter ties, or rafter ties shall be installed to provide a continuous tie. Ceiling joists shall be continuous or securely joined in accordance with Table R802.5.1(9) where they meet over interior partitions and are nailed to adjacent rafters to provide a continuous tie across the building where such joists are parallel to the rafters. Ht tp://newst ore.southe rnpine.Ceiling joists and rafters shall be nailed to each other in accordance with Table R802.5.1(9), and the rafter shall be nailed to the top wall plate in accordance with Table R602.3(1). I have marine/residential type structure in looking at the following manual (see link) how are the structures depicted exempt from joist end blocking? My question is whether anyone could justify joists that overlap and are nailed to eachother over a support provide restraint. Perhaps forming a scissor type truss with bracing members from the rafter at the wall end up to the collar tie or incorporating a wide top plate at the wall to give it rigidity from being thrust out from the deflection.Īnother question code (IBC) requires Joists to be laterally restrained at ends by blocking or other means. My question is not whether a rafter tie should be there it is whether it is explicitly required by code (IBC)? I was planning to engineer an alternative to keep the ceiling height higher. Rafters shall be sized based on the rafter spans in Tables R802.4.1(1) through R802.4.1(8). TABLE R802.5.1 (1) RAFTER SPANS FOR COMMON LUMBER SPECIES (Roof live load 20 psf, ceiling not attached to rafters, L/ 180) RAFTER. The rafter tie needs to be there to prevent thrust which has already pushed these walls out some. The braces shall be spaced not more than 4 feet (1219 mm) on center and the unbraced length of braces shall not exceed 8 feet (2438 mm). The pitch is 9:12 and the there is no rafter tie or ceiling joists. Spans for rafters shall be in accordance with Tables R802.5.1(1) through R802.5.1(8). For other grades and species and for other loading conditions, refer to the AF&PA Span Tables for Joists and Rafters. Table R802.5.1(2) Rafter Spans For Common Lumber Species (Roof live load 20 psf, ceiling attached to rafters, L/ 240). The span of each rafter shall be measured along the horizontal projection of the rafter. I have a conventionally framed roof with a collar tie in the upper third. Table R802.5.1(1) Rafter Spans For Common Lumber Species (Roof live load 20 psf, ceiling not attached to rafters, L/ 180). Spans for rafters shall be in accordance with Tables R802.5.1(1) through R802.5.1(8).
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