What is the Essence of a Two By Four?

Decades ago, common carpentry practice (later set in stone by written regulations) specified that certain applications needed a 2 inch by 4 inch board.   The reason this board was chosen was not due to its size per se (in most cases, for cost and space issues, I am sure folks would love to have gotten away with something smaller).  This size board was chosen for a specific application by its load-carrying ability.   For example, two inch by four inch boards spaced every 16 inches apart created acceptably strong framing for a wall.

Anyway, after many years of making lumber, the timber and lumber industry found ways to make the 2 inch by 4 inch board much stronger.  Well, not always stronger, but more uniform in strength such that the weakest board in a batch was much closer to the average than before.  But for standards, this has about the same effect -- 2 inch by 4 inch boards could be considered to be much stronger since the expected value had to be set at the minimum that might be encountered.

So now, all the standard applications are over-designed.  We can get away with a smaller, cheaper board than a 2x4.  Or, for those of you less focused on capitalism and more focused on environmentalism, we can use fewer trees to build the same house.  But how do we switch an entire industry that is steeped from birth as to what a 2x4 should be used for?  How do we rewrite a myriad of regulations that all call for a 2x4?

Well, in the lumber industry, they redefined the 2x4 to actually be something like 1.5 x 3.5 actual inches, a board which under new production processes has the same predicted strength as the old 2" by 4" boards.  In effect, they decided that the essence of a 2x4 was not its dimensions, but its load-carrying ability.  Almost any engineer can understand this immediately.  This means we still frame walls with 2x4's spaced every 16 inches, but the lumber is smaller and less expensive than it was before.  Standards and training don't have to change.  Architects maybe had to adjust a bit because their wall widths changed slightly, but a 3.5 inch board width actually is a nice number because with sheets of 3/4 inch drywall on both sides it makes for a nice round number 6" thick wall.

All of this is background to this absurd story, is using this history to try to commit legal blackmail against a couple large home store chains (via Overlawyered):

Two home improvements stores are accused of deceiving the buyers of four-by-four boards, the big brother to the ubiquitous two-by-four.

The alleged deception: Menards and Home Depot (HD) market and sell the hefty lumber as four-by-fours without specifying that the boards actually measure 3½ inches by 3½ inches.

The lawsuits against the retailers would-be class actions, filed within five days of each other in federal court for the Northern District of Illinois. Attorneys from the same Chicago law firm represent the plaintiffs in both cases. Each suit seeks more than $5 million.

“Defendant has received significant profits from its false marketing and sale of its dimensional lumber products,” the action against Menards contends.

“Defendant’s representations as to the dimension of these products were false and misleading,” the suit against Home Depot alleges.

The retailers say the allegations are bogus. It is common knowledge and longstanding industry practice, they say, that names such as two-by-four or four-by-four do not describe the width and thickness of those pieces of lumber.



  1. karl_lembke:

    So 0.5 = 1, for sufficiently large values of 0.5

  2. Geoff Jones:

    Interestingly to see the term 'board'. Over here in the UK a board is something that is thin compared to it's area so your 'drywall' we call plasterboard! Divided by a common language :-)

  3. Chris Retterath:

    My understanding is that a 2x4 was a rough dimension. Older houses will have these boards close to 2" x 4". But that lumber is un planed.

    With planing, the roughness is removed and you get a very smooth piece of timber. A plane is essentially a knife cut. The wood is as strong but nicer to work with. It can be marked easily.

    After the planing you get the standard sizes we've been using for decades. About 1.5 " by 3.5" for 2 x 4.

  4. Jamie:

    I don't understand your drywall math. A) 3.5 + .75 +.75 is 5 inches not 6 inches. B) where can you find 3/4" drywall? Not at any home improvement store I've ever seen. 1/2" for walls or 5/8" for ceilings or the occasional 1/4" for curved surfaces or skimming plaster.

  5. Craig:

    I learned that the 2x4 dimension applied to the green, un-planed board. Kiln-drying and planing shrinks the rough-cut timber.

  6. craftman:

    I can't see any reasonable application of purchasing lumber by volume that these lawyers even have a case. This feels like the tuna class action lawsuit where some company was underfilling its cans deliberately. But you don't eat lumber. You don't buy lumber to turn it into wood chips...?

  7. Bruce Zeuli:

    There is a charming, moving and slightly sexy movie that deals with this exact issue.
    It is about a strong of body and strong of mind older man who works to build a single story home for his loving though frail wife. He must fight regulators who won't let hime use the true dimentional lumber he grows and mills for himself. Wins court case and based on a true story.
    Title is Still Mine

  8. Matthew Slyfield:

    An the planing is done to ensure that the 2x4's are straight and smooth. Back when 2X4s were sold rough-cut, those using them for building anything normally had to take the time and the effort to hand plane the boards themselves,

  9. Griz Hebert:

    Wait until the plaintiffs learn a 16 penny nail has no pennies in it.

  10. Granja:

    If trial lawyers succeed, they'll next target Mercedes AMG. Their model numbers (43, 55, 63, 65) once matched engine displacement (L). Now the SL63 has a 5.5L engine and C43 a 3.0L, but make the same or more HP as the bigger engines they replace.

  11. Andrew_M_Garland:

    Next, sue McDonalds for selling a "Quarter Pounder" that definitely does not deliver a quarter pound of cooked beef. The weight is before cooking, just as the lumber is before planing.

  12. Ward Chartier:

    When I was taking wood shop in the mid-1960s I learned about this from the excellent instructor, Mr. Taylor.

  13. Craig:

    I was on the college track also at that time, but also took wood shop. I wish that I had taken metal shop and auto shop too. Everybody would benefit from these classes.

  14. auralay:

    There is the old joke about the mule that is docile and obedient, once the farmer "got his attention" by hitting him with a length of 2x4. Would 1.5 x 3.5 have the same effect? (This side of the pond we are now metricated to make measurements simpler. All I have to remember is that I need a 2400mm length of 35mm by 90mm. So much easier than 8ft of 2 x 4 planned all round. Not!)

  15. cc:

    Another similar type of suit claims that packaging larger than necessary is deceptive. Why are many packages for food etc much bigger than necessary? One reason is for visibility on the shelf. Another is to deter shoplifting. Such packages always have the weight on the front, but lawyers still go after them.

  16. markm:

    If you expect a 4x4 to actually be 4 inches, you aren't qualified to use one.

  17. ladyhawk:

    This statement immediately made me want to reply with a foul epithet. A great many people are DIY-ers who have not been to engineering school. Do we all NOT qualify to use a 2 by 4? Sounds like the most extreme form of snobbery. I have wondered for years why the lumber industry can get away with selling wood by its dimensions and then not providing something that attains those dimensions. And no one in the building supply stores that I have talked to about his has ever had an answer. Coyote thankfully did, without a hint of a sneer. Thanks Coyote.

  18. ladyhawk:

    Excellent film. Thanks for the reminder, I must go see it again.

  19. J K Brown:

    Wait till they discover that all the pre-fab hardware for a 4x4 magically fits the 3.5x3.5 dimensions. Items like post caps, anchors, hangers, etc.

    It's a conspiracy, I tell ya.

  20. captaincinders:

    Works just fine....until someone who is doing up their old house orders 2 x 4, 'cos that is what the house is built in.

    Actual conversation

    Me " Um...That 2 x 4 I ordered. I measured it and it is not 2 x 4. All my walls are 4 wide and it needs to be 4 to refurb them."
    Lumber Yard " Everyone knows that when you order 2 x 4, it is not actually 2 x 4. When you ordered the 2 x 4, you should have made it clear that you really wanted 2 x 4"

  21. MM:

    Has no one heard of "Nominal size"? The 2x4(nom) is actually 1-5/8 x 3-3/8, and that finished 4x4 is 3-3/8 on a side and called a post (usually). When working with old wood frame buildings (pre-1920 or so) you will learn the beauty of furring.

    The environmentalist movement has actually increased the amount of wood in walls since many localities have upped the level of insulation in exterior making 2x6 (nom) studs and plates the norm.

    I had to listen to my father lamenting the "new" skinny-er lumber way back in the 1950s.