All 2by's Are Not Created Equal
Kat and I recently took a trip to the local large home center store. Of course local for us is fifty mile trip one way. We wanted to compare prices and quality of lumber from the big boy stores and the local lumber yards (only 20 mile trip one way) to what we are harvesting and cutting (only two hundred feet one way).
When ever I embark upon a new project for building anything I always consult the bible. As I mentioned earlier it's the Machinist Handbook. In this universal reference book are tables and formulas for calculating strength of materials. It allows me to figure just how much force or weight I can place on something before it may break. Whether that force is logs, the wind or a snow load.
The very first thing I look at and that is required for these calculations are the actual cross section of the material to be used After that, of course, is the actual shape, square, rectangular, circular, tubular and how will the material be used, vertical or horizontal for load bearing purposes. One thing in common for all load calculations though, regardless of the above short list of factors, is the actual cross section of the material present.
One thing I have always been confused about is how can a 2x4 you purchase from the lumber yard or big box store be called a 2x4? Actually it measures only 1 1/2 x 3 1/2 and can be as small as a full 1/16th inch smaller than that. Of course this called a dimensional 2x4.
What we cut on our mill is called a full sized that measures a full measure of 2x4.
Lets look at the cross section of these two simple sized wood framing materials.
A dimensional 2x4 = 1 1/2 x 3 1/2 =
5 1/4 square inches.
A full sized = 2 x 4 =
8 square inches.
A dimensional 2x6 is actually
= 1 1/2 x 5 1/2 =
8 1/4 square inches.
A full sized 2x6 = 2 x 6 =
12 square inches.
What does the cross section measurement tell you?
I know what it is screaming to me.
Of course in strength calculations the quantity and size of knots must also be taken into account along with the species of wood.
So perhaps the next time you are at the local big box store or your local lumber yard, take the time to inspect those advertised specials of lumber.
Or better yet take the time to find a local miller in your area. That independent sawyer who will take the time and show you the strength of what real lumber will do.
I know when I use our 2x4 and 2x6 lumber there is no question about what will work and not work. I just look at the cross section.
