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Cross laminated timber for mass timber construction was developed relatively recently in the early 1990’s. Is there any technical reason this technique couldn’t have been utilized earlier? Is there some modern manufacturing process or modern adhesive used, or is it just that nobody thought to do it until then? Would the technology and adhesives available around 1940 allowed for mass timber construction?

Example, could the basic concept of this bridge been feasible 80 years ago? https://www.nordic.ca/en/projects/structures/mistissini-bridge

https://en.wikipedia.org/wiki/Cross-laminated_timber

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  • $\begingroup$ As some of the answers have mentioned, mass timber construction uses modern wood laminating technology. Are you trying to determine if these engineered wood products could have been invented earlier, or if the structures made with these products could have been made earlier? $\endgroup$ Commented Dec 27, 2021 at 18:58
  • $\begingroup$ The concepts would have been feasible, but people didn't need to think of them. The alternatives were readily available. There were still old growth forests that could be cut. The massive steel mills were the "new thing". People's perception was to use steel because it was a newer technology. $\endgroup$
    – David R
    Commented Dec 28, 2021 at 15:02

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80 years ago, yes, sure

Cross-laminated timber is a development of the old-school glued laminated timber (GLT); and GLT was made since the second half of the 19th century.

The conceptual difference is that in GLT the layers are laid with the fibers in the same direction, whereas in CLT they are laid with the fibers in perpendicular directions.

You also need modern resin glue, which became available in the 1920s.

And, of course, biggg presses.

Overall, by 1930 all the necessary stuff existed. Timber we had since forever, waterwheel powered saws were available since the Middle Ages, big presses were in use since the early 19th century, and strong water resistant glues were invented in the 1920s.

So that if they wanted to make cross-laminated timber in the 1930s, they could have made it.

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Plywood has been mentioned. I'd like to highlight a quite critical usage of a special plywood that is quite surprising for the modern worldview.

Plywood for the planes

Both US (duramold) and Soviets (the so-called "delta-wood") had technology to produce high-pressure wood-glue composites that were superior to the wood planks used in plane construction and comparable to then-available aluminum materials:

The I-301 airframe was partially made of "delta wood": a material composed of very thin (0.35–0.55 mm) layers of birch or pine wood veneer, and a phenol-formaldehyde resin known as VIAM-B-3, which together were baked at high temperatures and pressures. Delta wood was used for critical parts of the airframe. This novel construction material had tensile strength comparable to that of non-hardened aluminum alloys and only 30% lower than that of precipitation hardened D-1A grade duralumin. It was also incombustible and completely invulnerable to rot, with service life measured in decades in adverse conditions. During production of the prototype, it was discovered that the adhesive used in delta wood caused skin irritation and safety procedures needed to be devised for workers.

Source.

A fragment of a LaGG-3 fighter which spent 74 years on a river bottom and practically hasn't rot

Those developments happened before WW2, so, you have your 80 years. Actually, Soviets kept producing the rear props of their Mil helicopters of that stuff quite into the post-war time.

A Mi-6 tail rotor made from delta-wood after decades of service

Now, concerning the "mass" part: from the stats, at some point, Soviets managed to produce more than 16 LaGG-3's per day, I think that's as "mass-production" as it comes.

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    $\begingroup$ I added two illustrations to your post. I would recommend you to look up production costs for delta-wood compared to duralumin $\endgroup$
    – ain92
    Commented Dec 28, 2021 at 16:37
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Veneers have been around a long time.

Cross laminated timber seems to me to be plywood on steroids. https://en.wikipedia.org/wiki/Plywood

Plywood is a material manufactured from thin layers or "plies" of wood veneer that are glued together with adjacent layers having their wood grain rotated up to 90 degrees to one another

Coming at this from abject ignorance, I was surprised that no-one thought of making structural elements out of plywood before the 1990s. Indeed people did:

The design and testing of plywood girders Spiegelberg, Steven L.University of Wyoming. ProQuest Dissertations Publishing, 1965. EP19469.

But plywood goes back a lot farther. Wood made from multiple thin layers of wood glued together was done by ancient Egyptians.

https://www.veneering.net/history-of-wood-veneer/

The Ancient Egyptians also used wood veneers and created the first primitive versions of ‘plywood’ by taking the veneers and gluing them cross wise to each other.

veneered chair

The same link goes on to discuss the use of veneers in the European renaissance.

So the elements to make cross laminated timber were all in place in ancient Egypt and after. They could cut wood thin. They had glue and could glue thin sheets together to make a thicker one. They understood that altering the direction of the grain in successive sheets would result in a stronger product as regards withstanding stresses and shrinkage. As far as I can tell these laminated veneers were all used for decoration - They did not, as far as I know, use laminated veneer / plywood type products for structural applications. Although it is tough to know since those things would all be gone by now.


It is an interesting thing to me that this cross laminated timber can claim to be new as of the 1990s. Is the novel aspect the thick chunks? That Europeans came up with it? Worth more reading. But in any case I think there would be nothing keeping the Egyptians from making cross laminated timbers if they were inclined. Craftsmen familiar with veneers would catch on quick.

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    $\begingroup$ Cross-laminated timber is similar to plywood only in the sense that they are both made of layers of wood. No, you cannot make CLT with the techniques used for making plywood. You need biggg presses and modern glue. See how it is made. But! You can make CLT with the techiques used for making GLT (glue-laminated timber), except that you lay the layers at cross angles (so that the fibers run perpendicular in two consecutive layers) and you need modern resin glue (invented between the world wars). GLT was made since the 1860 or thereabouts. $\endgroup$
    – AlexP
    Commented Dec 27, 2021 at 18:36
  • $\begingroup$ This info is very helpful. I was aware of the long history of use of veneers, but obviously veneer is not a structural element, so I was uncertain show much the two techniques intersected. I also could not find any past examples of proof of concepts or experimental designs using cross lamented timber, which made me question if I was missing something, hence the question here. Thanks $\endgroup$ Commented Dec 27, 2021 at 18:37
  • $\begingroup$ @AlexP - that is a good video. Robots are cool and the results look improbably robust to just make walls out of! Solid wood walls 5 inches thick? I wonder though if you could (with much labor) not make comparable products using older glues together and traditional joinery like dovetails. $\endgroup$
    – Willk
    Commented Dec 27, 2021 at 19:17
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    $\begingroup$ Older glue no; you need strong, water resistant glue (and those big presses) or else you don't get the right structural strength. Traditional joinery, yes, but then what you get is dowel laminated timber (DLT), which is a differnt kind of engineered wood; sorry, I can only find a Wikipedia article in German -- Dübelholz. $\endgroup$
    – AlexP
    Commented Dec 27, 2021 at 20:10
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Probably due to a combination of requirements for the glue and for the gluing process, making cross laminated wood would have not been economically meaningful. Keep in mind that cost is still a shortcoming for cross laminated wood.

The adhesive is then applied to the timber, typically through a machine. Application of the adhesive must be airtight to ensure there are no holes or air gaps in the glue, and the adhesive must be applied at a constant rate. [...] Assembly pressing fully completes the adhering process. There are two main types of pressing methods, vacuum pressing and hydraulic pressing. In vacuum pressing more than one CLT panel can be pressed at one time making the process more time and energy efficient. Another advantage to vacuum pressing is that it can apply pressure to curved shaped CLT panels because of the way the pressure is distributed around the whole structure. With hydraulic pressing, advantages include higher pressures and the pressure placed on each edge can be specified.

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  • $\begingroup$ Thanks for the reply. I'm not terribly concerned with the economics, more just would it be technically feasible with the technology available at the time. For instance, as far as I know vacuum pressing and hydraulic pressing were utilized industrial processes for that time period. $\endgroup$ Commented Dec 27, 2021 at 18:05
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    $\begingroup$ @greenbeardj, you ask for mass production. Mass production doesn't happen at high costs. $\endgroup$
    – L.Dutch
    Commented Dec 27, 2021 at 18:09
  • $\begingroup$ 'Mass timber' is the name of the technique. thinkwood.com/blog/4-things-to-know-about-mass-timber $\endgroup$ Commented Dec 27, 2021 at 18:24
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As others point out, the idea of gluing wood together is not a new concept. Veneers (which are not structural in the slightest) have been around for thousands of years. Glue technology has been available for thousands of years too. Many early bows were a laminate of wood and bone. Egyptian sarcophagi made extensive use of glue.

I would argue that it wasn't the "knowing" but the "doing" that was difficult. Early glues were either rare (like those based on tar) or labor intensive (like animal glues) which made them expensive in comparison to other options. That is, why spend all the time and money to glue two boards together when using a whole timber or stone block will work? But expense is relative. If stone blocks or whole timbers are rare, then gluing scraps of wood together becomes an economic option. Another drawback is water proofing the joins. Animal glues dissolve in water, so any glued wood wouldn't last long in humid or wet climates without some major thought put in to the designs that would prevent water from eroding the glue.

In short, this is plausible, but not feasible.

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  • $\begingroup$ Cross-laminated timber is most definitely not made of "scraps of wood". On the contrary, the entire idea is to use perfect planks sawn of a full-size trunk and make them a better structural material. $\endgroup$
    – AlexP
    Commented Dec 27, 2021 at 22:44
  • $\begingroup$ @AlexP although to be fair compared to past builders who thought nothing of cutting down a 800 year old hardwood tree, we do have far less large timber to work with now $\endgroup$
    – John
    Commented Dec 28, 2021 at 1:06

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