The WWPA Lumber DesignEasy Joist/Rafter Spans application calculates allowable joist and rafter spans for structural grades in the major Western species, based on the size of the lumber and commonly used load and use parameters.
The entries in the input screen feature the following selections:
- Lumber Size: 2x4 up to 3x16
- LL (Live Load): Any value in pounds per square foot (PSF)
- DL (Dead Load): Any value in pounds per square foot (PSF)
- CD (Load Duration Factor): 1, 1.15 or 1.25
- L/Def (Live Load Span/Deflection Limit): 180, 240 or 360
- Incised?: Y or N
You can change any value and recalculate the spans when you press the Calculate button. The App will remember your inputs, so to compare species, touch the Species button, select a new species and the previously entered values will remain in the User Inputs screen. Simply touch the Calculate button again to generate a new table of allowable spans for that species and loading conditions.
For additional information on Western lumber, go to the WWPA web site at www2.wwpa.org.
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Lumber DesignEasy Joists/Rafters Spans
Developed by Western Wood Products Association.
Western Wood Products Association (WWPA) provides the Lumber DesignEasy - Joist/Rafters Spans application as is without any warranty of any kind, either express or implied.
All WWPA Lumber DesignEasy programs, like all commercial engineering software products, should be used as a tool, not a substitute for engineering judgments of design professionals.
Users of this program are responsible for verifying the suitability and applicability of outputs and results.
WWPA provides this program for informational purposes only and does not represent or warrant that any information provided in this program is correct, complete or up to date. WWPA may change or delete information in this program without notice at any time.
The WWPA Lumber DesignEasy programs may not be altered, modified or sold for commercial purposes. WWPA makes no warranties expressed or implied concerning this product. In no event will WWPA be liable for indirect, incidental, special or consequential damages, whether in contract, tort, strict liability or under any other legal theory arising from the use of the WWPA Lumber DesignEasy program.