Why is the 2 by 4 getting smaller and smaller?

This video explains why the 2 by 4 is getting smaller and smaller. The dimension has been modified several time over the last 100 years. There are several reasons that have driven this reduction over the years.

References
[1] The Forest Products Laboratory, "History of Yard Size Standards," U. S. Department of Agriculture, Madison, Wisconsin, 2964.
[2] R. S. Kellogg, Lumber and Its Uses, Chicago: The Radford Architectural Company, 1914.
[3] Canadian Wood Council, Wood Design Manual, Canadian Wood Council, 2017.
[4] J. Dinwoodie, Timber: Its nature and behaviour, London: BRE, 2000.

[TheEngineeringHub]

Notice how back in the day the corners of the boards were sharp. Now they are planed/chamfered. There are several reasons for this:
1. Chamfered edges help construction workers to avoid splinters and other minor injuries.
2. The rounded edges make it easier for the boards to slide and travel on the conveyor belts (during production) and are easier to stack.
3. The boards are (slightly) more fire resistant as the edges usually catch on fire first.

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[franceslarina]

Repeatedly the industry said, "without affecting the strength". I'd love to see a load capacity comparison between 100 year old 2" x 4" boards and the smaller modern stud boards with grain nowhere near as dense.

[stevencurtis]

My dad told me that 2x4s weren't 2x4 when I was a kid. Two words came out of my mouth: _"That's stupid."_ I stand by that assessment.

[leokimvideo]

Years ago I looked into why the Big Mac was getting smaller and it had nothing to do with shipping. it had everything to do with profits

[jacquesmertens]

We're encouraged to buy FSC certified, sustainable lumber. That's a good thing. But there's a flip side.
Until the early 1990's it was easy to buy slow grown, slow dried lumber, perfectly straight, heavy and incredibly strong. What's on the market today is fast grown, kiln dried, light as a feather and warped. It's not nearly as strong as the lumber we used to buy.
To compensate for the lower quality the size should increase, not decrease.

[CyclingSasquatch]

Spent 25 years in a house in the San Diego area that was built in 1898. All the studs were true 2x4", quartersawn old-growth redwood – absolutely stunning.

[slammingconcrete]

Man im glad i watched this video, as a carpenter it has always frustrated me having to work around different lumber widths and thickness but seeing this video, i cant imagine the rage and frustration being a builder or carpenter back when standards were being changed

[Jr-qols]

Those older cross sections show something else pretty important when evaluating lumber, which is how close the growth rings were back in the day compared to modern day lumber.

[yellowcrescent]

I worked in a southern pine sawmill from 2006 to 2009 -- from what I remember, most green-sawn lumber started out much closer to the stated dimensions (eg. 1.75" x 3.75"). It is then kiln-dried to a moisture content of around 8 to 15%, which causes it to shrink to about 1.70"x3.65" or so. After that, it is either then sold directly as rough lumber (usually for export only) or it goes to the Planer Mill. There, the dried boards are loaded, X-ray'd (to check for metal objects that could destroy planer blades), and then planed to final nominal dimension. The board is then re-measured for moisture content with an inline moisture meter, and re-measured for final dimensions with multiple laser curtains. It then goes to a grader line where the graders put special marks on the boards using big fluorescent colored crayon-type things, and these marks are read by an optical reader which causes the boards to get trimmed to final length (based on the marks, bad ends might get trimmed off), and then finally sorted into the appropriate bin. After each bin gets full, it is unloaded onto the final conveyor, auto-stacked on a palette, wrapped, tagged, and then stored in a warehouse/shed for loading onto a truck or train car.

Also, everything was recycled. All of the big wood chips were sold to nearby companies for making paper pulp or composites. And sawdust was used in the plant's furnace/boiler as fuel for producing steam for the steam kilns.

[nilsblackwell]

What a gold standard for clear explanation and not wasting any time. Kudos.

[kevintwiest]

I worked at a sawmill in the early '70s. At that time the finished product standards were changed to 1-1/2" X 3-1/2". Because mills were more accurate at the time, the rough cut standard was changed to 1-3/4" X 3-3/4" to reduce waste. this caused quite a stir at the mill because now all the saws had to be recalibrated for the standards of advancing the log on the carriage.

[fintux]

Even though in Finland we use the metric system, we still have certain lumber sizes often expressed in inches, though they aren't exact. But a two-by-four is 50 x 100 mm, which 1.97 x 3.94 inches. As far as I can tell, that is the size at which you purchase it in the store. So despite of getting rid of the units, we mostly kept the measures. In the US, the units were kept but the measures were not.

[shannonmikus]

Important to remember that the growers had access to old growth forests that had quality trees back when the 2x4 was first milled. The structural capacity of that old growth wood (particularly Southern Pine or SYP) was substantial. Once the greedy mills had raped the hills of all the useable trees, most of which were 100 years old or more, the hills were replanted with faster-growing varieties. Of course, none of the mills were willing to wait 100 years for a properly grown tree, so most replanted trees were cut at less than 40 years old. The consequence is that the poor soil, which was not allowed to "recharge" since it was replanted on bare soil (the natural consequence of clear cutting) and the trees that regrew had lower structural density. Thus, in the 1950s, during the post war building boom, engineers noted that SYP lumber was flexing more than their standards told them it should be. The growers/millers had to have the standard altered to match the weaker product they were producing. This altered the design of houses. Since there were no large beams anymore because trees were not being allowed to grow past 20 years in age, house design accommodated the inclusion of the weaker wood by creating the "balloon" frame house rather than the traditional post and beam method used prior to the 1950s. A balloon frame has thinner walls (weak 2x4s stacked closer together) and the new strengths standards were accepted and adopted. However, after mismanagement by the lumber companies, the trees continued to get weaker and weaker, so the standard was AGAIN lowered in the 1970s and house design had too change, again. Long spans disappeared. High ceilings went away, and the single story ranch house became the trade's only economical, structurally sound product. It does not end there. Continued demand for wood products outpaced the mis-managed tree farms' capacity to grow sturdy trees, and in the 1990s the lumber standard was lowered, again, and construction methods changed again. Now you can't even find a replacement wood joist to re-do the joists of a house built in the 1920s because the lumber of the same dimension, even custom cut, is much weaker than the original, so mid-span bracing is required.

It is true that today's houses really are just "mud and toothpicks" compared to the substantial, dimensional lumber frame houses that our parents grew up in.

So sad.

[flowerpt]

The combination of dimensional decrease and density decrease (fast-grown) has only led us to use 2x6 for anything but hanging drywall and small sheds. Some great old books have plans that aren't buildable anymore.

[ThePartarar]

I attempted building a deck and planter beds a few years ago with limited experience. I drew up crude plans, ran measurements, factored the cost, went to home depot, and was entirely confused to find the 2x4s weren’t actually 2x4”. Thank you for explaining lol.

[FTributo]

My childhood home in upstate New York was built in 1911. When it was remodeled in the 1990s, it was found that wall studs were actually a genuine 2" x 4". And the studs in the outside walls ran the entire 2-story height, maybe 25' at the longest.

[jakemakes]

Not only is new wood not as strong, but old growth wood just lasts forever. Facia board me and my dad installed on our house 12 years ago is already starting to break down, while I've seen siding on civil war era houses still in decent condition. The paint is pretty much gone, but that 100 year old wood is still rock solid. That dense grain is something else.

[ChristopherHallett]

My parents owned a house that was built sometime around the first world war - the framing was all jarrah in actual 2x4 size. When my Dad did some renovations he had to scour all the salvage yards in the region to find similar wood so the work he did would be just as sturdy as the original house.

[Efecretion]

For those wondering, 2x4 -> 1.5x3.5 is a 34% reduction in both volume and weight (for the same length of board).

[wramsey]

I recall our first house we purchased in Richmond, Indiana in 1987. The house had been constructed in 1926 and it was a high quality wood framed house. They had covered the exterior with wood planks, steel mesh then stucco. The stucco was still very hard and in great shape when we moved in. I recall over the next few years rewiring and replumbing the house. I lost count of how many spade drill bits i had to use drilling thru the wood for the projects. I measured the 2 x 4's and they were huge compared to today's standards, they in fact were 2" x 4" and strong and hard as an ox!!! Even many of the boards were oak and it took forever to bore a hole thru the floor joists with the smoke from the new drill bits lol!! They sure built quality houses back then, built to last!!! Oh yeah those floor joists were 2" x 12" spaced every 16 inches, that floor did not give at all when you walked on it. Makes you miss the quality of those days.