Why is lumber say at home depot in sizes like 2x4 when it is not that size . In old construction i have found some wood that is 2’x4’ when did the change come about and why?
It’s about one and a half by three and a half. I believe the wood is two by four inches when first cut from the timber, then about half an inch is taken off for planing and smoothing.
Welcome to the SDMB Lumber Board!
“Standard dimension lumber sizes produced in North America are listed as surfaced dry sizes (19 percent moisture content or less) in the table below. The availability of lumber sizes varies somewhat according to the area of the country from which the raw material originates. Lengths up to 6.1 m ( 20’ ) are commonly available from western Canada and up to 4.9m (16’) from eastern Canada. Longer lengths are available on special order. They are also available in the form of fingerjoined lumber.”
Surfaced Dry(S-Dry), Size, mm - 38 x 89
Surfaced Dry (S- Dry), Size, in. (actual) - 1.5 x 3.5
Rough Sawn Size, in. (nom.) - 2 x 4
A “2x4” is the actual rough sawn size prior finishing and drying.
Source: http://www.cwc.ca/products/lumber/visually_graded/sizes.html
“Dimension lumber is identified by nominal sizes of rough lumber. Lumber that has been planed for a smooth surface has actual sizes that are less than the nominal sizes.”
That sounds good, but it doesn’t explain why the 2 x 4 keeps shrinking over the years. Originally, it was the actual size of the board. Later, it was the nominal size. Then the nominal size kept shrinking. At one time, a 2x4 was 1.75 x 3.75; now it’s 1.5 x 3.5.
The real reason, of course, is the smaller the 2x4, the more of them you can cut from a log. The more you cut, the more money you make from that log.
You can still buy “rough cut” lumber that will be the exact dimensions listed. But I’ve only used it for rough framing or things like sawhorses.
IIRC The government requires a minimum size for the boards. When the minimum size was first introduced, mills had a habit of varying wildly due to the non-precise nature of their equipment. As the process was refined and the equipment consistant, the mills made it a point to be as close to the minimum as possible (so, as was mentioned earlier, they could get as many boards from the tree as possible) With the hi tech equipment now used in mills, each log is cut differently because a computer has already figured out the perfect number and type of boards to cut.
What pisses me off, and I have been seeing it more and more, is that I am seeing more and more boards that are bark boards, were whole sides are bark. Sure, they are stud grade, but these clearly don’t fall within the prescribed measurements. Where the hell is the enforcement?