variation in lumber dimensions
variation in lumber dimensions
(OP)
I'm working on an existing building that has number 3 lumber. The depths are all over the place - 2x12's range in depth from 10.5" to 11.25" Is this a function of the poor grade of lumber or is there something else?






RE: variation in lumber dimensions
Mike Halloran
Pembroke Pines, FL, USA
RE: variation in lumber dimensions
In twenty years I have never seen a 2x12 less than 11.25"...give or take a few 1/16ths.
I have worked on some old buildings that had hardwood lumber 2x12's that were actually 2" x 12".
RE: variation in lumber dimensions
This is nothing new SEIT.
Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask
RE: variation in lumber dimensions
Aside from the getting them to be level, this amounts to a 23% difference in I, and a 15% difference in S. That seems significant to me! Doesn't the AF&PA (or whoever is in charge of this) have dimensional tolerances that need to be met? Is this true for any grade of lumber - that it can really vary that much?
RE: variation in lumber dimensions
I can say for #2 SPF and SYP, I never saw variations on that level.
Mike-If you are talking about I-joists, yes, I much preferred them as well. They saved a lot of time. Often times they were made to span front to back on the house eliminating the lapping of conventional lumber. They had electrical knock-outs, the top flange was much wider than 1.5" making sheathing a breeze, nailing them to the sill plates was a breeze...etc, etc. etc. But, When the price OSB shot threw the roof a few years ago, they disappeared, and so did I from framing.
Not behind desk rotting :)
RE: variation in lumber dimensions
RE: variation in lumber dimensions
It got to the point, and he was using HF#1 or DF#2 material, that he had to rip the joists to the least common size, so your strength and deflection concerns are very valid. You can tolerate 1/4", but not 3/4.
Time to generate new span-load tables!
Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask
RE: variation in lumber dimensions
Have you confirmed grade stamps on the lumber?
I am assuming you are talking SYP. Flipping quickly through the grading guide gives no such latitude to have a #3 2x12 be anything less than the 11.25" minimum.
Maybe you have a fat run of 2x10's?
RE: variation in lumber dimensions
RE: variation in lumber dimensions
Check to see if some of these were ripped for clearance of something.
I agree...that's a lot of variation. Even in older buildings, that would be a bit unusual. As TJ noted, lumber is not usually undersized.
RE: variation in lumber dimensions
It sounds like you may have a mix of dry cut lumber and green cut. With the green cut giving a 11.5"(1-.035)= 11.1" to 11.5"(1-.13)= 10" dry heights.
Garth Dreger PE
AZ Phoenix area
RE: variation in lumber dimensions
Garth Dreger PE
AZ Phoenix area
RE: variation in lumber dimensions
BA
RE: variation in lumber dimensions
RE: variation in lumber dimensions
RE: variation in lumber dimensions
Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask
RE: variation in lumber dimensions
RE: variation in lumber dimensions
Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask