Expert: Dan Griffin - 3/2/2010

Question
QUESTION: We are building a single story log home. The rim joists are 3(2x10x16). Floor joist spacing is 16 inches on center with span of 14 feet. Joists will be doubled under all load bearing walls. My builder wants to double every other joist throughout the home. Is this normal?

ANSWER: Dan,This sounds a bit unusual unless he has a specific reason.  A standard span table here:
<http://www.awc.org/calculators/span/calc/timbercalcstyle.asp?species=Southern+Pi>
shows #2 Yellow Pine able to span 16'.  I am confused about your comment on load bearing walls.  By definition, none of the walls that parallel the joists can be load bearing.  Why are the rim joists tripled?  This, again, is quite unusual.

---------- FOLLOW-UP ----------

QUESTION: Wow, thanks for the quick response. The rim joists were required by the log company. We are stacking 6x 12 square logs. My mistake on the load bearing walls. I meant to say joists under wall partitions. Not sure why he wanted to place doubled joist every 32 inches. I thought that was a little overkill. I could understand every 48 inches maybe. So, I should be ok sticking with single joists on 16 inch centers, doubled under standing walls?  I really appreciate your help. Thanks again!

Answer
The only reasons I can think of for estra joists would be known concentrated loads or using a different grde or species of lumber that is not rated for the span. Do realize that codes and span tables deal with minimums.  It never hurts to exceed minimums, but I would think going to closer centers or going up a lumber size or grade or going to TJL's would be a better approach.