Is 2×6 lumber heavy?
This is actually fairly important, not just to determine how many boards can be toted around a jobsite by one person, but also in calculating the dead loads which must be carried by structural members such as roof trusses and rafters.
Like most things played around with by engineers, and other people with too much time on their hands, there is a formula to calculate this (please feel free to scream in anguish now):
62.4 X [ G / (1 + G X 0.009) X (m.c.)] X [1 + m.c./100]
Whoo Hoo!! If this isn’t fun…..like watching paint dry?!
Seriously, it is not so tough. G is the value of the Specific Gravity of a known species of lumber. In the U.S. the most popular choices for framing lumber are Southern Pine (G=0.55), Douglas Fir-Larch (G=0.50), Hem-Fir (G=0.43) and Spruce-Pine-Fir (G=0.42).
The moisture content of the lumber is expressed as the “m.c.” above. Lumber stamped as “dry” has a maximum moisture content of 19%.
Picking Dry Hem-Fir and filling the appropriate blanks into the formula gives, 62.4 * [.43 / (1 + .43 * 0.009 * .19)] * [ 1 + (.19/100)] = 26.86 pcf (pounds per cubic foot). So a 12 inch cube of dry Hem-Fir should weigh 26.86 pounds.
A cubic foot has 1728 cubic inches (ci). 2×6 has finished dimensions of 1-1/2 inches by 5-1/2”, or 99 ci in lineal a foot. Taking the weight calculated above (26.86 pcf) dividing by 1728 and multiplying by 99, gives the weight of a foot of Hem-Fir 2×6 as 1.539 pounds (lbs).
Want to pack around 12 foot long 2×6 lumber? In Hem-Fir, it will weigh 18.466 lbs.
Think of dead loads as the weights of materials which are permanent. In the case of a typical pole barn roof, purlins will always be there supporting the roof sheathing.
If purlins are placed two foot on center, up the slope (or run) of the roof, the dead load attributed to the purlins can be determined by dividing the weight per lineal foot (1.539 lbs calculated above) by the spacing of the purlin (in feet) divided by the cosine of the roof slope. In this case, it is roughly 0.81 psf (pounds per square foot).
Not a lot of weight, but it still must be accounted for. As well, 60% of dead load weight can also be used to counteract the forces of uplift.
So much for the math lesson of the day.
Now, aren’t you glad you asked?
There are a few more than 144 cubic inches in a cubic foot, about 12 times more.
board foot?
Anthony ~
I appreciate when readers are astute enough to catch an error! The answer is right, just both cases are missing a multiplier of 12.
It should read:
A cubic foot has 1728 cubic inches (ci). A 2×6 has finished dimensions of 1-1/2 inches by 5-1/2”, or 99 ci in a lineal foot. Taking the weight calculated above (26.86 pcf) dividing by 1728 and multiplying by 99, gives the weight of a foot of Hem-Fir 2×6 as 1.539 pounds (lbs).
Very interesting approach to calculating . Now I can figure out any lumber size. Thanks a lot. What’s your background if I may ask.
Here is my story: https://www.hansenpolebuildings.com/2011/06/before-the-pole-barn-guru/
Why not just answer the question
For example
Not knowing the weight
How much does a 2x6x10 weigh ?
A 2x6x10 in pine weighs 8 lbs
In pressure treated approximately 12 lbs
Im not looking for a formula
It would be easier to go to lowes with a scale
Than a formula
Your answer to how much a 2×6 weighs
Is great for some
But not your average
Thank you for your comments. A table would become quite large in a hurry and the idea is to show what is actually involved. By the way – your 2x6x10 in Southern Pine would weigh in over double what your estimate is and if pressure treated it would depend if it was dried after treating or not.
Thanks for the info…what does the constant of 62.4 represent? Is that static for any woo and dimension?
62.4 is the density of water in pounds per cubic foot.
what dose a 2x6x8 presure treated weigh?
It will vary greatly depending upon level of treatment, if it was dried after treating and how long it has been since it was treated. It could weigh double what untreated dry lumber weighs.
I did the calculation pcf and I don’t get 26.86. Reviewing your formula, I see your parenthesis are not balanced:
62.4 * [.43 / (1 + .43(0.009)(.19)] * [ 1 + (.19/100)]
Inside the first set of square brackets [ ] you have open parenthesis. If I enter the expression exactly as you have it, then my calculator gratuitously adds an extra parenthesis at the end and I get the 26.86; however, if I resolve the missing parenthesis inside the first set of square brackets as follows, (which matches the formula you gave)
62.4 * [.43 / (1 + .43(0.009))(.19)] * [ 1 + (.19/100)],
I get 5.088 which seems much more reasonable to me. I would not expect a chunk of wood roughly the size of a basket ball (1 cubic foot) to weight 28 lbs, 5 lbs seems more reasonable.
The 26.86 pcf is absolutely correct (a cubic foot is a much larger chunk of wood than one might imagine)