This table, from Span Tables for Joists and Rafters, gives the required values for various design conditions; an addendum that comes with Design Values for Joists and Rafters gives the valies for specific species. 0000003003 00000 n Buckinghamshire HP14 4ND UK t: +44 (0)1494 569600 f: +44 (0)1494 565487 w: www.trada.co.uk e: information@trada.co.uk. Then drop down to find the appropriate Fb value for the span. In order to establish proper sizes, grades and on-center spacing of joists and rafters you first need to determine what loading is acceptable to the building code. Wind uplift capacity values are given for three conditions, i.e. The values in Tables 1 and 2 are generated assuming dry conditions, normal duration of load and untreated, Exposure 1, structural pan-els. ft. Dead load of attic floor when floored = 20 lbs. 0000026480 00000 n Joists, and rafters must be strong enough not to break when loaded. This information is found in the code book. The tables shown here are excerpts from the hem-fir, Douglas fir-larch, and spruce-pine-fir tables. The loads are based on adjusted roof snow loads from the governing building code. The loads carried by floor joists, ceiling joists, and rafters are transferred through their end points to supporting walls and beams. replacement roof details Actions Permanent Load Roof finishes Permanent Formwork F100 Gauge 1.2 350mm thick concrete slab (584+0.05x25) Total permanent load 0.30 kN/m 2 0.19 kN/m 2 7.09 kN/m 2 7.58 kN/m 2 Services General services Variable Load Imposed load on roof (UDL) Imposed load on roof (PL) Construction Load Snow The fact that snow loads only act part of the year has been taken into account in the rafter tables, but don't forget to use the "Snow Loading" column to get the Fb design value. These may include: Dead loads- from the self weight of the roof construction. The fact that snow loads only act part of the year has been used to create the rafter tables. Visit the roof framing page for more information on cutting roof rafters, and visit the roof pitch calculator for … The following table provides typical weights (dead load, self-weight) for various roofing materials. Second, use the snow load value for your region in determining which rafter table to use. 101 34 Transcripts from Previous IBC … 134 0 obj <>stream For other conditions, the loads should be appropriately adjusted using the factors given. Typical Design Dead Loads 3 Dead Load Adjustments Adjustments are made in the dis-tribution of dead loads due to the placement of utility lines under the floor system and fixtures (lightsfloor system and fixtures (lights, ducts, etc.) 101 0 obj <> endobj Snow loading. Unlike the trussed roof, live load and dead load of the rafters and ceiling joists must be accounted for as separate systems. But lack of stiffness leads to costly problems. ASCE Revision Calendar. ft. when used for storage only) Dead load of attic floor, not floored = 10 lbs. For a floor system you can find the individual weights of drywall, strapping, floor joists, subfloor, underlayment and carpet in an architectural handbook like Architectural Graphic Standards. Determine the uniform load acting on the interior truss, if the trusses are 6ft-0in on center. This publication has a much more extensive offering of possible joist and rafter conditions. To put this in context, Max permissible clear spans for joists for flat roofs with unlimited access Imposed load 1.50 kN/m2. For example southern pine is much stronger and stiffer than spruce. Unlike stiffness, live loads and dead loads are added together to determine minimum design values for strength. Table 2 demonstrates the differences in the dead load capacity required within a roof structure when comparing minimum and maximum substrate establishing. Use the horizontal projection of a rafter, not its actual length, when figuring rafter span, These documents provide an expanded view of span-table use through "explanation" and "commentary" sections at the beginning and end of the publications. Remember when your science teacher said: every action has an opposite and equal reaction? per sq. I find the AWC documents easy to follow. A higher grade of a given species has a higher strength rating (Fb) and often has a higher stiffness value (E) too. Table 9.1 in Span Tables for Joists and Rafters (Figure 5) gives a required compression value of 237 psi for a span of 16 feet and bearing length of 1.5 inches. Simply reference Span Tables for Joists and Rafters published by the American Wood Council (AWC). roof loads. As a beam bends the outermost (extreme) fibers are compressed along the top edge. 0000003050 00000 n Dead loads. For this, use the tables in Design Values for Joists and Rafters. Stiffness of structural members is limited by maximum allowable deflection. 0000003191 00000 n Often, 2x10 joists spaced 24-inches o.c. The house acts as a structural system resisting dead loads (weight of materials), live loads (weights imposed by use and occupancy), like snow loads and wind loads. AWC lists the required compression perpendicular to grain values for joists and rafters for various spans, on-center spacing and loading conditions in its Span Tables for Joists and Rafters. When the imposed load is considered as an accompanying action, in accordance with EN 1990, only one of the two factors Ψ (EN 1990, Table A1.1) and αn (6.3.1.2 (11)) shall be applied. Duration of load. 0000012242 00000 n per sq. 0000003643 00000 n When the imposed load is considered as an accompanying action, in accordance with EN 1990, only one of the two factors Ψ (EN 1990, Table … Benchmark values are multiplied by 1.15 to yield snow-load values and by 1.25 for 7-day loading. The values for dead loads in Table 3.2 are for commonly used materials and … Check to see that the lumber species selected has the necessary compression strength perpendicular to the grain. Their design span, the exact length from face to face of the supports, is 15 feet 1 inch (see illustration - Figure 1). For roof live loads less than 20 pounds per square foot (psf), rafter spans and required E values tabulated for 20 psf shall be permitted to be adjusted in accordance with the fol-lowing table: For roof live loads … You can contact the AWC Help desk at 1-202-463-4713 or via email at, Southern Forest Products Association Span Tables, Western Wood Products Association Span Tables. E is a ratio that relates the amount a given load causes a material to deform. This table is for a dead load of more than 0.25 but not more than 0.50 and allows for an imposed loading of no more than 1.5 kN/sq.m. And at the same time, fibers stretch along the bottom edge. Dead Loads, cont’d Typical Weights of Horizontal Systems •Roof Construction –Asphalt Shingles ~ 15 psf (pounds per sq. ft. Live load on attic floor = local requirements. An Fb value indicates design strength for those extreme fibers. Step 3 Wood Design Values: Now you must select a wood species and grade that meets the required Fb and E values, and that's available in your area. Figure 4 (Usually 30 lbs. Floor Dead Load Calculation : Carpet & Pad : 3.00: psf: Conc o/ stl deck : 35.00: psf: Joists : wt/ft : 16.00: plf : spacing: 5.83: ft : Jst Wt : 2.74: psf: Ceiling : 1.80: psf: Misc : 1.46: psf: Total Unit Weight : 44: psf: Note that this calculation does not include the weight of any girders or other structure that is in the floor system. 0000008917 00000 n “load arrangement which describes the load of the snow layer on the roof resulting from a snow deposition pattern which has an exceptionally infrequent likelihood of occurring” These load arrangements (treated in Annex B of EN 1991-1-3) may result from wind redistribution of snow deposited during single snow events. Strength and stiffness are equally important. Span is the distance from face to face of the supports. The code book can be purchased through your local code official. You can contact the AWC Help desk at 1-202-463-4713 or via email at info@awc.org. Let's say you're building a 16-foot addition and have to select the correct size and species of lumber for the floor joists. %PDF-1.4 %���� I find the AWC documents easy to follow. Dead loads (kN/m2) excluding self-weight of joist – not more than 0.50 kN/m2 = 3.27m. For the most part, live load and dead load values for floor and roof systems are considered distributed loads. Table of Contents ASC Steel Deck is leading the way in innovation with ongoing a result, the printed catalog may not contain/reflect the latest test results and values of our products. Step 4 Bearing Check: The final step is to make sure the lumber you've chosen meets the required design value for compression perpendicular to the grain. For example, Appendix A indicates that one type of clay tile roof system has a live load value of 20 psf and a dead load value of 15 psf. In other words, the weight is distributed or shared uniformly by the members in the floor or roof system. 0000047205 00000 n Surveyors’ span tables for designing roof rafters. For upper floors with 22mm thick chipboard decking and a 12.5mm plasterboard ceiling: a dead load of between 0.25kN/m² and 0.5kN/m² may be assumed Figure 6 The values in Tables 1 and 2 are generated assuming dry conditions, normal duration of load and untreated, Exposure 1, structural pan-els. In order to establish proper sizes, grades and on-center spacing of joists and rafters you first need to determine what loading is acceptable to the building code. If your code book says your snow load is 40 psf, then you use the 40 psf live load rafter table. The span of a rafter is not based on the measurement along its length. 22. Roof Slab R-17, Ex-1 to 2 14 Snow loading S-1 to S-2 15 Wind loading WL-1 to WL- 6 16 Proposed Roof Plan and details Drawings 3095/003/1010, 1011 and 5010 Structural Calculations - Code and Standard Used BS EN 1990 : Basic of Structural Design BS EN 1991 : Actions on Structure BS EN 1992 : Designs of Concrete Structure 0000002909 00000 n For this example, I've excerpted the relevant sections from tables for hem-fir, Douglas fir-larch, and spruce-pine-fir (Figure 4). Roof Construction: Light-frame wood roof with wood structural panel sheathing and 1/2-inch gypsum board ceiling (2 psf) with asphalt shin... Home; Courses; Articles; Downloads; Solution Manuals; Log in; Register; Preparing for FE or PE exam? Beams, studs, joists and rafters act as a structural skeleton and must be strong enough and stiff enough to resist these loads. Dead loads are static forces that are relatively constant for an extended time; usually the weight of materials plus immovable fixtures such as carpet, roof and etc. Joist span Bridging Girder load width Half joist span Live load on roof = local requirements for wind and snow. Joists, and rafters must be strong enough not to break when loaded. Tables automatically handle this adjustment. Figure 2