![]() It is dependable for everything from building a deck to framing a five-story residential complex and everything in between including flooring, marine construction, material handling, furniture, permanent wood foundations, post-frame construction. Special Engineering Note: Open Joist trusses may be manufactured with components that provide increased structural values that may exceed the performance levels indicated in these charts. Southern Pine is one of the most sustainable and often long-term cost-effective options.NOTE: Clear spans shown on this chart are presented under the following conditions: (1) Bearing size varies and is determined by loading conditions, truss span and truss spacing (2) "Strongback" bracing is not considered (3) Assumes composite action with a single layer of 3/4" wood sheathing glued and nailed or screwed (4) Spans are clear distance between supports for uniformly loaded trusses and include allowable increases for repetitive use members.To find maximum clear span for a given truss depth in a given loading condition, refer to the bottom line of spans shown for that particular truss depth. Allowable span tables are provided to simplify the selection of rafter and ceiling joist size for wood roof framing and cold-formed steel framing. This chapter contains two roof-ceiling framing systems: wood framing and cold-formed steel framing. Maximum spans published on the chart above may be limited by standard joist configuration. User note: About this chapter: Chapter 8 addresses the design and construction of roof-ceiling systems. * Because OPEN JOIST is a "stock" product, the length of an OPEN JOIST truss determines the size and grade of the truss' chords (see table below). As EWP designers, we understand that our customers and builders have their preferences regarding permanent Dead Load Deflection.View details on fire resistance assemblies for one and two hour endurance. The tabulated rafter spans assume that ceiling joists are located at the bottom of the attic space or that some other method of resisting the outward push of the rafters on the bearing walls, such as rafter ties, is provided at that location.Other span tables are based on the guidance given in BS 5268-7.1 which is a uniformly distributed load of 1.5kN/m² for spans greater than 2400 mm and 3.6 kN load per metre width of floor for spans less than 2400 mm to ensure that very small joist. Table R301.9-1/4" Depth Maximum Live Load Deflection (L/360 & L/480, 1-1/2" Minimum Bearing Each End)ġ1-1/4" Depth Maximum Live Load Deflection - (L/360 & L/480, 1-1/2" Minimum Bearing Each End)ġ1-7/8" Depth Maximum Live Load Deflection - (L/360 & L/480, 1-1/2" Minimum Bearing Each End)ġ4" Depth Maximum Live Load Deflection - (L/360 & L/480, 1-1/2" Minimum Bearing Each End)ġ6" Depth Maximum Live Load Deflection - (L/360 & L/480, 1-1/2" Minimum Bearing Each End)ġ8" Depth Maximum Live Load Deflection - (L/360 & L/480, 1-1/2" Minimum Bearing Each End)Ģ0" Depth Maximum Live Load Deflection - (L/360 & L/480, 1-1/2" Minimum Bearing Each End) Rafters Purlin Span tables Domestic floor joists Imposed load 1.5 kN/m², C16 timber. If that same joist had gypsum ceiling (L/240), the allowable deflection is 0.6". Rafter Span Table with Different Spacing (IRC 2021) The span of a rafter is the horizontal length it covers from the point of its placement to where it ends. For example, the allowable deflection of a 12ft span floor joist with plaster (L/360) is 0.4" (12ft divided by 360). Always consult Eurocode 5 Span Tables when calculating spans. Note it gives the allowable deflection based on a fractional span quantity, so a larger denominator will yield less deflection. Span calculations derived from the American Wood Councils 'Span. ![]() SPFs is a grouping of wood species (Eastern Spruces, Balsam Fir, Red Pine, Jack Pine, Englemann Spruce, Lodgepole Pine, and Sitka Spruce). ![]() ![]() Maximum spans are inside to inside of bearings. Typically for better performing floors minimal defection is desired.Ĭhapter 3 of the International Residential Code (IRC) provides the maximum allowable deflection for a given structural member (floor, roof, wall, etc.). Note: Deflection is limited to the span in inches divided by 240 for live load only. joists indicate the need for one A3 angle per rafter. The amount of flex depends on the magnitude of the load applied, span of the member, and stiffness of the member. where x is span divided by live load deflection (both in inches). Allowable deflection is generally expressed as a fraction of the span, in inches.Īll structural members will deflect or flex under load. Deflection is the bending or "sag" caused by loading. ![]()
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