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Southern yellow pine rafter span tables4/30/2024 So I have to run more piggyback joists to take the weight. Jack Rafter Infill rafter installed to continue the roof line - fixed from wall. I have 2x8's #1 spruce on 16" centers holding up the wood floor above my basement, and although my dead-load estimates said I could hold 4 more layers of gypsum, the building inspector (actually the plans examiner) said that 2 was the maximum additional load. I trust your 2圆's don't have anything on top of them that they are also holding up (like a floor).īTW, someone here posted that one shouldn't go right up to the dead load limit, but rather one should leave a wide margin for error (e.g. if you have a 2圆, which is really 5.5" tall, then you can have a 1.8" diameter round drilled hole in the middle.) There's a building code somewhere that says that any notches in the middle third are illegal.ĭrilled holes in the vertical middle of the joist can occupy the middle third without too much trouble (i.e. So if the notch were 1", then treat the beam as a 2x5 for the length (not that you'll find specs for a 2x5 anywhere, although there are specs for 2x4s). if a 2圆 were 12' feet long, then the middle third would be the middle 4') then treat the entire joist as the remaining thickness of the joist where the notch is. applications according to the 2018 International Residential Code. southern pine and spruce-pine-fir and required number of jack studs). If you cut a notch in the middle third (i.e. These rafter span tables provide the best reference to quickly and easily determine the maximum span for all grades of southern pine according to the 2018 International Residential Code. Live load is anything that's temporary like people stomping around (i.e. I think dead load is whatever's on top of the floor that doesn't move, plus the weight of the joists, plus whatever else you're holding up (pipe, insulation), plus the weight of the gypsum. The spans in these tables were determined on the same basis as the code-recognized Span Tables for Joists & Rafters and Wood Structural Design Data. Also, try this link for a handy calculator. I actually have my PE in civil engineering, however I specialize in environmental engineering so its been a while since I calculated beam loadings. The allowable span, on 12" centers, appears to be 12'-3" - although this is probably not a big deal for your purposes since the deflection rating (L/360) is based on a 30 psf live load in addition to a 10 psf dead load. However, it appears that you slightly extended your allowable span for defelection purposes (if using southern pine). 2圆 joists, even with notches cut out, should be more than sufficient to support a second layer of drywall - whether on 12 or 16 inch centers. Remember your loading on the joist depends on the spacing on center. Joists and rafters shall be sized according to AF&PA Span Tables for Joists and Rafters. This way you can easily calculate the load placed on a linear foot of beam (joist). 2 grade of Southern Pine, Douglas Fir-Larch, Hem-Fir or Spruce-Pine-Fir. When calculating loads, it is more appropriate to calculate psf. Personally I'd see which way would be cheaper overall.I think 1/2 drywall is rated at approx. But he could also use 2圆's if he dropped down to 16" centers. Southern Forest Products Association Span Tables. Use the span tables in the links below to determine the maximum allowable lengths of joists and rafters. Given minimal snow load, using L/180 and a 10psf dead and 30psf live load, and white pine lumber, he would need 2x8's which are good to 11' on 24" centers. The Southern Forest Products Association’s span tables for Southern Pine headers and beams provides an easy method for selecting the proper Southern Pine header or beam for its intended application. So, it sounds like the OP is only spanning 10' on 24" centers. For more than 300 years, Southern Pine headers and beams have framed millions of windows and doors and supported just as many floor joist systems. Live load is anything added, like wind, snow, funature, people, etc. Dead is the weight of the beams and structure itself. 5", thus a larger beam is required for the same span. Same span in a floor joist would only be allowed to deflect. So using L/180, a 15' span (180") would be allowed to deflect 1" at its mid point and still be considered within limits. L/240 is typically ceiling/rafters that are going to be finished on the underside. Which is simply how much the joist/rafter is allowed to bend/deflect. First thing to consider is the deflection limitations. Their is pleanty that go into sizing rafters. The SFPAs tables list maximum spans for Southern Pine joists and rafters assumes the quality of wood products and fasteners, and the design of load-supporting. Definatally overkill:laughing: but it sure beats going too small:thumbsup:īut your rule of thumb is not too bad for floor joists, which must be a little more stout than rafters.
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