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View Full Version : When a 2x4 WAS a 2x4


obbn
08-05-2014, 02:21 AM
Hello Everyone,

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?

Measure for Measure
08-05-2014, 02:26 AM
The Master speaks: Why aren't two-by-fours two inches by four inches? (http://www.straightdope.com/columns/read/3074/why-arent-two-by-fours-two-inches-by-four-inches)

Summary:
Modern sizes were agreed to 1963. A 2x4 isn't two by four inches unless you use the magic phrase which is, "True size".

Terr
08-05-2014, 02:31 AM
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.

aceplace57
08-05-2014, 02:59 AM
Just wait until you discover wall studs aren't eight foot. Sheetrock and plywood is 8 ft but studs at home depot (http://www.homedepot.com/p/Unbranded-2-in-x-4-in-x-92-5-8-in-Kiln-Dried-Whitewood-Stud-569062/202093349) 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.

davida03801
08-05-2014, 06:48 AM
Find out where a local small time sawmill is. There you can get "real" 2x4 and other dimensional lumber sizes.

Around these here parts in northern New England, I can think of 2 within an 30 minute drive.

Quercus
08-05-2014, 07:14 AM
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.
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.

John Mace
08-05-2014, 08:46 AM
You know that 1/2" plywood you buy at Depot? It's 15/32". Sell enough, and that 1/32" is profit!

FluffyBob
08-05-2014, 09:40 AM
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.

John Mace
08-05-2014, 10:41 AM
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.

Yes, I should have said the stuff is actually labeled correctly. But if you ask for 3/4" ply, they will show you the 23/32" stuff.

gotpasswords
08-05-2014, 12:40 PM
"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.

usedtobe
08-06-2014, 12:49 AM
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...

RememberMe
08-06-2014, 01:39 PM
Just wait until you discover wall studs aren't eight foot. Sheetrock and plywood is 8 ft but studs at home depot (http://www.homedepot.com/p/Unbranded-2-in-x-4-in-x-92-5-8-in-Kiln-Dried-Whitewood-Stud-569062/202093349) 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.

True, until you look at the stack to the right where you see the pile of true 96" 2x4s.