![]() ![]() Roof joist spacing has requirements or factors, including the rafter size, rafter span. FIGURE R802.5.1 BRACED RAFTER CONSTRUCTION TABLE R802.5. rafter spacing is determined by the prescriptive tables. H R = Height of roof ridge measured vertically above the top of the rafter support walls. span, use the longest span to determine hole location in either span. H C = Height of ceiling joists or rafter ties measured vertically above the top of the rafter support walls. Example: In the joist span table below, the highlighted cell (10-5) indicates that a 2 grade 2' x 8' Douglas Fir joist, spaced 24' apart, can have a maximum span of 10 feet - 5 inches (10-5) if designing for a live load of 40 PSF, a dead load of 10 PSF, and a deflection limit of the total span in inches divided by 360. Note: Where ceiling joist s run perpendicular to the rafter, rafter ties shall be installed in accordance with Section R802.3.1. Qualified students are those who are full-time students enrolled in a wood design course at a university or college. (Pricing for Span Tables and Design Values for Joists and Rafters 2005 Combo) Non-member 14.00. Table 3.4.4.1b Maximum acceptable bearer span (continuous span) - bearers supporting a timber floor and non-loadbearing stud wall. For pre-1960 construction, the rafter span tables are based on structural calculations with lumber sizes and wood species and grade appropriate for older. A tutorial for using the span tables is also available. (Uninhabitable attics with limited storage, live load = 20 psf, L/Δ = 240) CEILING JOIST SPACING (inches)įor SI: 1 inch = 25.4 mm, 1 foot = 305 mm, 1 degree = 0.018 rad. Table 3.4.4.0a Effective member spacing for structural steel bearers and strutting beamsSingle spanning rafter or joist. Span table based on WWPA Western Lumber Span Tables, Edition 2/94. (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.įor SI: 1 inch= 25.4 mm, 1 foot= 304.8 mm, 1 pound per square foot= 0.0479 kPa.Ī. Those using this on-line calculator assume all liability and hold PLIB harmless from its use.Shall be in accordance with Tables R802.4(1) and R802.4(2).įor other grades and species and for other loading conditions,ĬEILING JOIST SPANS FOR COMMON LUMBER SPECIES ![]() ![]() Neither PLIB nor its members assume any responsibility for any particular design prepared from this on-line calculator. Allowable span tables are provided to simplify the selection of rafter and ceiling joist. The span of each rafter shall be measured along the horizontal projection of the rafter. PLIB believes the information generated by this calculator is accurate and conforms with design standards referenced by U.S. framing systems: wood framing and cold-formed steel framing. 17 and/or the National Design Specification (NDS) Supplement published by the American Wood Council for adjustment factors. For other service conditions or load conditions, see paragraph 200 a-l in WCLB Standard No. In calculating the design values, the change in strength and stiffness that occurs as lumber dries has been taken into consideration as well as the reducing in size that occurs when unseasoned lumber shrinks. Additionally, compression perpendicular to grain design values (F c) are included as a consideration for selection of joists and rafters. Note: The design values shown in the table are for normal load duration and dry service conditions and are applicable to lumber surfaced either unseasoned (S-GRN) or dry (S-DRY or KD). SCOPE hese span tables for joists and rafters are calculated T on the basis of a series of modulus of elasticity (E) and bending design values (F b).
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