My wife and I are in the process of rebuilding a horse stable on our property. We are putting on a new metal roof. While taking down the old one we discovered one of the A frames was rotting, so we pulled the board off to replace it. It looked to me like a 2x4, but it seemed a bit too big. To be on the safe side I brought it with us down to Lowes to purchase a replacement. Imagine my surprise when the wood guy down at Lowes saw the board and his eyes lit up! He exclaimed, “now that’s a real board”. He said they don’t make them like that any more. We measured it and found it was a true 2x4, not the roughly 1 1/2 x 4 pieces sold today.
The stable was, to my best estimate, built sometime in the late 30’s or 40’s. So my question is, when did a 2x4 cease being a 2x4 and why the change?
AFAIU (I am not an expert) the timber is “rough-cut” into exactly 2"x4" beams. If you go to the place where that is done, and specifically request the rough-cut beams, you can buy them and they will be 2"x4". But you will have to handle them carefully or you will get splinters galore. I was also told that because of all the nooks and crannies they rot easier, but I don’t know how true that is.
To smooth them out, they are put through what I think are called “planers”. Those result in beams that have smooth sides, but cost you 1/2" in each dimension. So you get 1 1/2" by 3 1/2". Or so.
Just wait until you discover wall studs aren’t eight foot. Sheetrock and plywood is 8 ft butstuds at home depot are 92 5/8 in not 96 inches. Thats because they fit between the 2x4 top and bottom plates.
Quite convenient if you’re framing walls. But you probably want 8ft stock for top and bottom plates. Or basic wood projects.
That’s the theory-- and how it was done in the old days – but modern saws and planers are more efficient and don’t lose a whole quarter inch on each side. So a modern sawmill will rough cut their nominal 2x4s smaller than 2"x4".
Only of academic interest unless you want a real 2"x4", in which case you should know you probably couldn’t just take a standard rough cut from a modern mill.
Weird thing is John OSB subfloor is actually labelled as 23/32", where as a lot of panel goods used in cabinetry (where a 1/32" actually does matter) will be labelled 3/4" but be somewhat less, perhaps a European 18mm, but often a nonsensical weird size. Some products truly are their nominal size.
Dimensional number width is generally reliable in the smaller sizes, so a 2x4s are usually within 1/8" of 3 1/2", and studs or premium lumber should be a consistent 3 1/2". Larger sizes can vary by a 1/4" and are 3/4" smaller than the nominal size on average. Length is a whole other matter, while studs will be a reliable 104 5/8 or 92 5/8, 8’ material can vary by half an inch in length.
In homes built up to the mid sixties I find a lot of variation in stud width, so I suspect drying techniques got a lot better at some point there.
“3/4-inch” plywood has been shrunk down for so long that tool makers produce 23/32" bits for routers in order to make properly-sized dados (slots or grooves) when building furniture.
I don’t know offhand when or why 3/4 shrank to 23/32. Neither dimension has a clean metric equivalent. Most plywood for furniture and cabinetmaking is sanded both sizes, so that could easily account for 1/64" off each side, but that doesn’t explain the shrinkage in rougher stuff used for roof decking and subfloors. Probably another case of “It’s good enough” and when you’re making a million square feet of the stuff, that 1/32 adds up.
And a “Gallon” of paint stopped being a gallon decades ago - the ounce or two they cheat you is explained as “leaving room for the tint” - when we were putting a real gallon of paint in the can, you were getting that 1-2 ounces “too much” at the mixing station.
Just bend over and spread 'em - soon Twitter will disover it has been giving you more than youve been paying for…