Originally Posted By: Clevy
Originally Posted By: bepperb
The Sagulator is what I use. To be honest there isn't a huge difference and I just assume everything the same. The only time I would think otherwise is with OSB/MDF/plywood which have considerably more sag.
http://www.woodbin.com/calcs/sagulator.htm
Anyway, I think you'll find that softwoods are at least 75% as rigid. No way a 1x3 oak is as strong as a 2x4 fir.
Osb is nothing like mdf and mdf is nothing like plywood.
And they will only sag if over-spanned.
Sheathing like osb is way stronger than any dimensional equivalent.
Your post is in every way wrong. Please save yourself the carpal tunnel and stick to what you know because wood isn't it.
I've got span tables for everything from 2x4 to 12x12 timbers in one of my old carpentry books however they are obsolete because today we use nothing but engineered materials for floors and roofs.
My point was that I treat all wood the same, the exception would be for the odb/mdf/plywood where I do not. I'm not sure if I wrote it poorly, if you have poor reading comprehension, or if you were just too excited to win at the internet and couldn't help yourself.
Anyway, my purposes are furniture, not construction, and an MDF/osb shelf will sag considerably more than a solid lumber equivalent. And that's the only thing relevant to my work. But if someone took, say an Oak shelf and wanted it in paint grade poplar I wouldn't think twice about substituting in the same design.
I guess my advice to the OP would be that it might depend on the application and who you talk to.
Clevy, pop a Xanax and a baby aspirin and chill.