Wood Sizes

[Lissa Hall]

So saw a post on how wood sizes have changed over years. Was this strictly about money on. Companies  behalf or was there more to it. Example why a 2x4 is not a 2x4.

[Gene Howe]

Money is one factor but, modern milling practices are the main reason. 

[John Morris]

Here ya go Lissa, I saw that same one and thought it very interesting.

I found an explanation from the originator of the actual image.

 

 

Why a 2x4 isn't 2 inches x 4 inches?
Answering this question requires a bit of history about the evolution of lumber standards. As our country developed during the 18th and 19th centuries, sawmills sprang up to satisfy local demand for construction lumber. This lumber was not kiln dried (called green) and was supplied roughly sawn from the mill.
Lumber sizes varied by region because mills produced lumber based on local building customs and demand. Before 1895, no standards existed for the grading and sizing of lumber, though two inches had evolved over time as the most common rough thickness for joists, rafters, and studs and one inch as the most common thickness for boards.
During the second half of the 19th century, the wood products industry realized that they could broaden their markets geographically using the rapidly developing railroad system, which forced them to produce sizes matching the distant markets they supplied. Also, they realized that shipping green lumber (which was much heavier) was much costlier than shipping dry lumber. So, kiln drying of lumber became more common.
Like a cotton T-shirt, lumber shrinks with drying, and the once rough, green, full-sized 2 x 4 becomes smaller. Though dry lumber has the added advantage of staying straighter at the jobsite, the different drying rates of the various species of lumber being shipped around meant that there was still considerable variability in lumber sizes. The advent of surface milling, or planning, helped the move towards a more uniform (though smaller) size and easier-to-handle lumber (a smooth surface meant less splinters for carpenters). However, it wasn't until 1969 that the U.S. Department of Commerce once and for all unified lumber sizes across the country. So, the once full-sized 2x4 was reduced to today's 1-1/2 x 3-1/2 through a combination of drying, machining, as well as unifying the wide variety of species used to make the ubiquitous 2x4.

 

Source: Bob Falk, FPL wood engineer

[Fred W. Hargis Jr]

Didn't someone sue one of the big box stores because their 2x4s weren't really2x4? Seems like I remember such a thing.

[Gene Howe]

2 minutes ago, Fred W. Hargis Jr said:

Didn't someone sue one of the big box stores because their 2x4s weren't really2x4? Seems like I remember such a thing.

Yeah, caused them to label them with the actual sizes.  

[John Morris]

4 minutes ago, Fred W. Hargis Jr said:

Didn't someone sue one of the big box stores because their 2x4s weren't really2x4? Seems like I remember such a thing.

I remember that too Fred, don't know how far it went, but I want to say that lawsuit may have been responsible for the actual metric size and fractional inch display on the cards.

[Gunny]

It was a suit brought by a homeowner that didn't know anything about wood but tried to build something.  It appears they also did not know of a invention called the tape measure.  

 

And as a result we now have such lumber listed as 2x4 with the nominal size listed as well.

 

Plywood is now listed in fractions of 16ths or 32sec.  In this regard metric would be easier for a larger percentage of people to understand. A education issue I'm my opinion.

 

Example 13 mm is 1/2  19mm would be 3/4. 

 

I know the crossover sizes because in automotive we use that alot.  Others will know for various reasons. But the majority of the population would be clueless.

[Lissa Hall]

So basically starts out as 2x4?? But shrinks?? Probably didn't understand correctly my mind has been kinda messed lately

[PostalTom]

Plywood is a completely different issue.  Being dimensionally stable, there is no need to make a 3/4" thick sheet of plywood 23/32" instead of 24/32".  At least none that I have heard.  4 x 8 is usually 4 x 8, except for, I believe, MDF, which in my experience is actually 49" by 97".  The reason I have read for that is that MDF chips and dings easily on the edges, so the  extra inch in both dimensions give some room to trim to a clean edge.  I think the thinner plywood is actually a plot by the router bit manufacturers to be able to sell router bits matching the thinner sheets.  What does everyone else think?

[Gunny]

2 hours ago, Lissa Hall said:

So basically starts out as 2x4?? But shrinks?? Probably didn't understand correctly my mind has been kinda messed lately

Yes. They put it in a kiln to dry the wood. When it is done currently you get a 1 1/2 x 3 1/2 inch size.

[Fred W. Hargis Jr]

2 hours ago, Lissa Hall said:

So basically starts out as 2x4?? But shrinks?? Probably didn't understand correctly my mind has been kinda messed lately

It does shrink when it's dried, but the bigger issue is that the rough cut is 2x4, then the drying and milling (planing and jointing to get everything uniform) takes to the size we have now.

 

7 minutes ago, PostalTom said:

Plywood is a completely different issue.  Being dimensionally stable, there is no need to make a 3/4" thick sheet of plywood 23/32" instead of 24/32".  At least none that I have heard.  4 x 8 is usually 4 x 8, except for, I believe, MDF, which in my experience is actually 49" by 97".  The reason I have read for that is that MDF chips and dings easily on the edges, so the  extra inch in both dimensions give some room to trim to a clean edge.  I think the thinner plywood is actually a plot by the router bit manufacturers to be able to sell router bits matching the thinner sheets.  What does everyone else think?

I thought the reason it wasn't 3/4" anymore was that they started cutting the face veneers so thin (to gte more veneer out of the log) it reduced the thickness of the ply. But I do buy cabinet grade plywood from Columbia Forest Products that's 48.5x 96.5 allowing you trim the edges slightly.

Edited May 23, 2020 by Fred W. Hargis Jr

[Gene Howe]

Most Baltic Birch ply comes in 5'X5' sheets. I've seen it in 4'X8' in rare instances. Thicknesses are usually quoted in mm. It's been so long ago that I've bought any hardwood ply that I don't know if the sizes have changed. 

[FlGatorwood]

Thank you, Lisa, for creating this thread.  I had the thought that it was only greed from companies.  Thank you, John, for making it clear about the process of how the lumber actually shrinks, but it is also sanded and routed on the corners, which reduces the size.  Now, I am wondering if these new standards are of equivalent strength as the old actual 2" X 4".  Does anyone know if the strength is the same or if it has significantly changed?

[Gunny]

4 minutes ago, FlGatorwood said:

Now, I am wondering if these new standards are of equivalent strength as the old actual 2" X 4"

I have been told yes in fact better.  BUT, they are using quick grown trees not old growth trees.  So I am doubting that claim.  

[Gerald]

Something to consider when buying hardwood in my understanding is that the board foot is calculated based on size from the kiln before planing is done( if you buy S4S)

[PeteM]

18 hours ago, FlGatorwood said:

  Now, I am wondering if these new standards are of equivalent strength as the old actual 2" X 4".  Does anyone know if the strength is the same or if it has significantly changed?

Sometime about 1990 there was a revision in the allowable strength calcs for structural wood (and I think specifically "fir" types) that caused a stir (the de-rating was severe....50%?).  I don't think it was caused by any nominal dimension change, though.  

[John Morris]

12 hours ago, Gerald said:

Something to consider when buying hardwood in my understanding is that the board foot is calculated based on size from the kiln before planing is done( if you buy S4S)

That's right Gerald, I know when I buy 4/4 from my local hardwood dealer, it is 3/4" net. Yet it's advertised as 4/4, and it's S3S. If I want a true 1" I purchase 5/4 and so on.

[Gene Howe]

Most of my lumber is rough, live edged stuff. My mesquite supplier will cut any thickness specified. But, it ain't S4S by any means. My two favorite wood suppliers for other than mesquite, stock both rough cuts and dimensional hardwood. When the rough stuff is listed as 4/4, by golly, that's what it is! 

I'm retired, rough cuts are less expensive, I rather enjoy the prepping process, and, I have the time. Did I mention that I'm retired. 

Edited May 24, 2020 by Gene Howe

[Gunny]

13 minutes ago, Gene Howe said:

Did I mention that I'm retired. 

Makes me sick!!!!!!

[John Morris]

25 minutes ago, Gene Howe said:

I rather enjoy the prepping process,

Me too Gene, sadly the sawmill I used to get lumber from, we had a falling out, so I don't go there anymore. So I'm left with the only hardwood dealer within a 40 mile radius, they cater to the cabinet shops yet they do have a very extensive line of hardwood.

Here they are in a topic I created a while back.