Replies

1. 
   Guest_ | Jun 26, 1999 02:15pm | #1

   *
   None as far as I'm aware, however there is a difference between seasoned and unseasoned.

1. 
   Guest_ | Jun 26, 1999 06:42pm | #2

   *One thing to consider is grading the lumber. Spans increase for higher grades, not the way the lumber is surfaced. It always blows the building inspectors mind to see rough cut beams or logs used for structural purposes. I guess it's because they don't usually come with a grade stamp.

1. 
   Guest_ | Jun 26, 1999 07:18pm | #3

   *Tedd,

   Simplified Engineering for Architects and Builders by Harry Parker is a great resource of information. I would highly recommend purchasing this book.

   Joseph FuscoView Image

1. 
   Guest_ | Jun 26, 1999 11:42pm | #4

   *The only difference would be the resulting increase in section properties based on the rough dimensions, which may result in a slighty longer span, but the increase is going to small so I would just use the span tables for the grade of lumber you have as if it was dimensioned lumber.Dave

1. 
   Guest_ | Jun 27, 1999 11:13pm | #5

   *Not what I hoped to hear :-)Actually, AWPI equates rough sawn 2X's lumber to suitable alternative replacing 3X's for intermediate rafter-supporting, girder plates on pole buildings for 15' pole center to center span (about 14' 1" plate edge to plate edge span). But they didn't give any explanations on this.I also have a DYI book on pole building that says rough sawn lumer is about 15% stronger than finished lumber. Where I live the difference is 1/2' thicker and deeper. I was presuming that a 15% increase in strength would calculate out to 15% increase in span-ability.tedd

2. 
   Guest_ | Jun 27, 1999 11:14pm | #6

   *Not what I hoped to hear :-)Actually, AWPI equates rough sawn 2X's as suitable alternative replacing finished 3X's for intermediate rafter-supporting, girder plates on pole buildings for 15' pole center to center span (about 14' 1" plate edge to plate edge span). But they didn't give any explanations on this.I also have a DYI book on pole building that says rough sawn lumer is about 15% stronger than finished lumber. Where I live the difference is 1/2' thicker and deeper. I was presuming that a 15% increase in strength would calculate out to 15% increase in span-ability.tedd

3. 
   Guest_ | Jun 28, 1999 01:47am | #7

   *When spans are calculated, real as opposed to nominal dimensions are used. Therefore, rough lumber of the same species and grade will be stronger, but not by a fixed percentage. If you are using tables for spans I would not figure any more for rough lumber than surfaced lumber. But, I assume that the rough lumber is for exposed use. If so then your allowed deflection will be 1/240 of the span rather than 1/360 for dry wall or plaster below, so you could get away with a greater span. If you are cutting things this close, though, you are probably making a mistake.

4. 
   Guest_ | Jun 28, 1999 08:26am | #8

   *Actually I was considering rough sawn 2X10's for rafter and joist carrying girders to make a wider plate surface. You might be right about cutting things too close as the span is right at maximum according to tables and I plan also to us rough sawn joists/rafters which will increase the weight the girders will have to carry.

5. 
   Guest_ | Jun 30, 1999 01:19am | #9

   *I would second what kcoyner said regarding grading. A lot of rough cut lumber isn't graded, and you may have some defects which would downgrade your lumber. It could actually span LESS than surfaced lumber, depending on the grade/species. Just a thought. - jb

6. 
   Guest_ | Jul 08, 1999 10:40pm | #10

   *....would ditto Joe Fusco's comment about Simplified Engineering ...... spent a semester with it as the main text last year ...... excellent book ...... there's also a companion study guide that's very usefull, too. NELMA (www.nelma.org)(Northeastern Lumber Manufacturer's Association) has a span chart that includes spans for hemlock and pine as well as spruce/fir and ungraded lumber. If I recall correctly, spans were less for ungraded lumber.

7. 
   Guest_ | Jul 09, 1999 10:18am | #11

   *In other words, commercial interests of industry take precedent over truth, once again.

8. 
   Guest_ | Jul 10, 1999 08:54pm | #12

   *I asked the same question in my Strength of Materials class last year......we did the math and because of the increase in physical size, there is a increase in spanning abilty ....but that assumes equivalent grade. I use a fair amount of rough cut lumber and find you have to be careful ..... the quality varies greatly, even from the same mill. I think industry errs on the side of caution (the cover your rear end principle)...... you and I may pick through our boards but many don't.