Expert: Dan Griffin - 5/27/2009

Question
I am a homeowner who is currently undergoing a two story addition in Florida.  My architectural plans call for Southern yellow pine grade 2 for all lumber.  I noticed that many of the floor trusses have No.3 stamped on them.  Before I speeak with the contractor, I want to be prepared for what to stand for.  Is grade 3 acceptable for floor trusses?  If not, should he have to redo this work if it indeed was an error?  Please help!!

Answer
Christy, you are calling them trusses.  I suspect you mean joists as trusses would be made of multiple boards pinned to each other.

The grade of lumber certainly makes a difference.  Here is a standard span table to give you some idea of the issues:
http://www.awc.org/calculators/span/calc/timbercalcstyle.asp

go to the pull down arrow at each item to get the choices.

Make the items say:  
Species - Southern Pine
Size (I don't know, dimension lumber is 1/2" smaller than its    nominal   size = a 2x8 is 7 1/2" tall by 1 1/2 wide)
Grade - check it at #3 and again at #2
Member type - floor joist
Deflection limit - L/360 is code minimum, L/480 is stiffer and quieter
Spacing - the distance between joists
Live load - 40# is code minimum except in some few bedroom situations which will allow 30#
Dead load - 10# is normal
This will calculate the maximum span for this lumber.  Span measures between bearing points.  If the span is even one inch farther than the calculation, it is NOT acceptable.

It does not change the fact that your plans called for #2 lumber, that is what should have been bid, that is what you should receive.  I would make him tear it out or adjust his cost if and only if the #3 lumber meets the span limits.  Do not let him bamboozle you.  A city code authority or your architect should be more than willing to enforce the issue.