cities out of wood
October 9, 2018 10:05 AM   Subscribe

The Case for Making Cities Out of Wood. Alphabet's (nee Google) Sidewalk Labs proposal for Toronto's Quayside development may be The world's largest timber project. Heavy timber construction is becoming popular, with project in France , Vancouver, Amherst, and planned for more, like Tokyo. The Race for the Wood Skyscraper Starts Here. Mass Timber 101. Can building codes keep up?

The wood from the trees: The use of timber in construction, Ramage et al., Renewable and Sustainable Energy Reviews, Volume 68, Part 1, February 2017, Pages 333-359.
Trees, and their derivative products, have been used by societies around the world for thousands of years. Contemporary construction of tall buildings from timber, in whole or in part, suggests a growing interest in the potential for building with wood at a scale not previously attainable. As wood is the only significant building material that is grown, we have a natural inclination that building in wood is good for the environment. But under what conditions is this really the case? The environmental benefits of using timber are not straightforward; although it is a natural product, a large amount of energy is used to dry and process it. Much of this can come from the biomass of the tree itself, but that requires investment in plant, which is not always possible in an industry that is widely distributed among many small producers. And what should we build with wood? Are skyscrapers in timber a good use of this natural resource, or are there other aspects of civil and structural engineering, or large-scale infrastructure, that would be a better use of wood? Here, we consider a holistic picture ranging in scale from the science of the cell wall to the engineering and global policies that could maximise forestry and timber construction as a boon to both people and the planet.
The Incredible Lightness Of Heavy Timber has some definitions of Gluelam, CLT, and more. Mass Timber is in for massive change. Sustainability of Mass Timber Buildings. Is mass timber really sustainable? Cross Laminated Timber Can Reduce the Carbon Footprint of New Buildings

The mass timber revolution is coming

previously: The Case For Tall Wood Buildings
posted by the man of twists and turns (25 comments total) 19 users marked this as a favorite
 
If it can be done right (meaning with safety factors that meet or exceed current standards) I personally am all for using more wood in construction. Wood is a renewable, rapidly-replenishing resource. Yes, the logging industry is environmentally problematic—but nothing like the mining industry. Lumber is at least potentially a sustainable resource, and when harvested for construction and then re-grown, trees function as a pretty good carbon sink too.
posted by Anticipation Of A New Lover's Arrival, The at 10:11 AM on October 9 [5 favorites]


Well if growing it means it's environmentally sustainable, bone has 2.5 times the compressive strength.

Solicitors welcome at side entrance, haven't seen that before.

I have heard that large timbers survive fire better than steel.
posted by BrotherCaine at 10:28 AM on October 9


Bare steel? Sure. Protected steel? Concrete reinforcing steel? Maybe not.
posted by LionIndex at 10:34 AM on October 9 [2 favorites]


Aside from the wood issue, not everyone is on board with googles dream of “someone to give us a city and put us in charge.” Sidewalk Toronto has only one beneficiary, and it is not Toronto
posted by rodlymight at 10:55 AM on October 9 [6 favorites]


Jet fuel can't melt wood beams.
posted by tobascodagama at 11:16 AM on October 9 [4 favorites]


The carbon balance is addressed in a couple supporting articles. In short: heavy timber like this probably works out somewhere around carbon neutral right now, with the actual positive or negative outcome varying by factors that may change as the business scales. If nothing else it's less of an atmospheric carbon contributor than production of steel or concrete, and the wood that isn't consumed in production (as sawdust, burned as fuel, or other waste) is a long term carbon sink. Once you make an engineered material out of it (e.g. heavy timber), the carbon in that wood isn't really going anywhere.

Fire safety is also addressed in numerous articles. The fire performance of heavy timber (nominal dimensions of 4 × 6" or bigger) is at least as good as steel and concrete. When exposed to flame it forms a char layer and maintains structural strength for longer than steel typically does; concrete spalls or cracks at high temperatures and can lose strength pretty quickly. Also the long history we all know of large fires fed by wood buildings predates modern fire suppression systems. If you had two equally tall buildings with equally effective fire suppression systems, the wood building might actually be safer than the steel one, because wood takes longer to fail.

Most of these things were already true when I took an architectural materials class in 1990. Wood by itself is a surprisingly good building material. Do some science to it and get something even better. Who would have guessed?
posted by fedward at 11:30 AM on October 9 [8 favorites]


In Oregon we had a contextualizing incident: https://www.statesmanjournal.com/story/news/2018/08/13/collapse-oregon-state-project-trouble-clt-industry/981611002/
(sorry I don't know how to make links work in meta filter, the link button never works for me)

You might find a bright shiny new thing but the old corrupt world is still here.
posted by Pembquist at 11:44 AM on October 9 [1 favorite]


It'd be interesting to see a sprinkler study; some years back a neighbor had their sprinkler system go off in their wood frame house, and while that meant the house didn't burn down, the house was still effectively destroyed (all the floors warped, and a couple of the walls went out of plumb).

...which is perhaps merely a testament to a crappy tract house (and turned me off the idea of installing active fire suppression in my house), but nevertheless I'd be interested to see a full-scale test.

On the Oregon CLT problem linked above, seems like a competent QA/QC program should have prevented that problem? Is there a nondestructive test for these panels? There'd better be, if they want them to see large-scale adoption.
posted by aramaic at 11:58 AM on October 9 [2 favorites]


Are these skyscrapers being built in the assumption that the fickle eyes of future architectural style will tear them down long before they rot and collapse? What about preserving unique examples of period construction for subsequent generations?

Past civilisations no doubt made fantastic wood structures as well, but all we know of them now are boxy outlines in aerial radar maps
posted by CynicalKnight at 1:01 PM on October 9


In Oregon we had a contextualizing incident

It is not hard to determine how the author of that article feels about CLT. Even so, writing the contract in such a way it was effectively single-sourced to a vendor without much experience seems like a pretty big problem, even if it was done as a way to jump start local industry.

seems like a competent QA/QC program should have prevented that problem

Indeed, even with a single source contract they shouldn't have had those problems. A lot of the construction industry is (supposedly) self-policing, though. There have been lots of recent problems with concrete in construction projects connected to the DC area transit authority (WMATA), so those in particular are fresh in my mind. A new line extension was plagued by faulty concrete with falsified inspection reports; a new transit center had seemingly endless problems with its concrete, also with (you guessed it) improper and fraudulent inspections. Things that should be caught often aren't, and the regulatory bodies that are supposed to catch them are underfunded and stretched for time and resources. Sometimes stuff still gets caught before it's too late; sometimes it doesn't.
posted by fedward at 1:13 PM on October 9 [1 favorite]


I just came from a wood recycling workshop last week where CLT was a hot topic. Adding to the benefit of solid wood as a carbon sink, there are many groups looking at CLT as a market opportunity for wood residues that are currently being wasted or underutilized. Basically, this idea eliminates concerns about the logging industry, because wood could instead be sourced from things like removed urban trees that are typically landfilled or mulched.
posted by hessie at 1:16 PM on October 9 [1 favorite]


There are timber buildings in Japan from the first century AD, and barring any unfortunate natural disasters, there's no reason to think that they won't make it to their 2,000th birthday. So timber as a building material is fine. The biggest threat to it, historically, was fire, and that's largely been mitigated with modern fire suppression systems, and steel buildings are vulnerable to it also (idiot "Truthers" to the contrary, fire will soften steel beams to the point of collapse).

The insurance industry is aware of this, and the premiums you'd pay on a timber warehouse with good fire suppression isn't that much higher than a steel-truss warehouse. (There are a surprising number of timber warehouses in the US, many built during wartime steel shortages.) I've been told that heavy wood timbers can actually last longer in a fire than uninsulated steel trusses, because the steel will deform and cause truss failure when the geometry changes, while the wood will char but still retain most of its strength until enough of it burns through (typically 1.5"/hr is the standard rate used in estimates).

Anyway... the timber being considered for skyscrapers isn't the massive solid-wood timbers of shinto temples or 1940s warehouses, it's typically engineered products. Some are, by weight, if not mostly glue than a lot glue. So I'm curious about the recyclability aspect. It's possible to make a material that's actually too durable—e.g. Trabant body shells made of Duroplast are notoriously durable, to the point of being a nuisance and disposal problem. In contrast, steel is almost infinitely recyclable, and the recycling rate of structural steel is 96% according to the USGS, without any sort of incentivization other than the inherent efficiencies of the process. That's pretty impressive, and I can't tell if the sustainability analyses are looking at the carbon footprint of steel produced from primary (i.e. from iron ore using basic oxygen furnaces) or secondary (re-melted scrap, i.e. "mini-mill") sources. They are quite different, and in the industrialized world we would probably be self-sufficient without primary steel production at all (setting aside if that would be a good idea for a variety of reasons), if we didn't export scrap.
posted by Kadin2048 at 1:50 PM on October 9 [6 favorites]


Wood by itself is a surprisingly good building material.

A shipwright I once knew liked to refer to wood as "the original carbon-fiber-reinforced, resin-based composite."
posted by Anticipation Of A New Lover's Arrival, The at 4:14 PM on October 9 [12 favorites]


Wood is a great material, unless you live somewhere perpetually damp - then it rots. Timber buildings are only guaranteed for 30 - 40 years here, because damp.

I can totally see how it's a much better building material in better climates though. Steel beams need to be double clad in plasterboard for fire safety regulations while wooden beams don't - because wooden beams can burn slowly whilst steal beams melt.
posted by stillnocturnal at 4:39 PM on October 9


Steel beams need to be double clad in plasterboard for fire safety

Mildly offtopic, but that's not the only way to protect 'em. There's also spray applied materials (butt-fugly, but cheap as heck), mastics (mainly used in industrial environments and on offshore rigs, as they can be resistant to the excitingly-named "jet fire"), intumescents (pricey but looks nice), and a couple more esoteric approaches (mainly "engineered fire resistance" which involves ugly math to prove that the unprotected steel will be sufficiently strong for a given unit of time for a given fire exposure, and specialized products like Fire-Trol columns).

Intumescent is pretty popular in Europe, but quite rare in the US (much to the chagrin of manufacturers).

Also, in North American practice for certain ratings you can use a single layer of drywall, and if not then there's fire-resistant drywall rather than two layers of normal drywall. For example, to protect my wood garage (attached to house), I put in the fire-resistant drywall (throughout, not merely on the separation wall, out of paranoia and a desire to be thorough, not because code required it for an existing structure).
posted by aramaic at 5:43 PM on October 9 [3 favorites]


Wood is a great material, unless you live somewhere perpetually damp - then it rots. Timber buildings are only guaranteed for 30 - 40 years here, because damp.

I don't know what guarantees you are talking about but timber buildings last hundreds of years if properly maintained. Boston and the Pacific Northwest, for example, are plenty damp.
posted by JackFlash at 5:45 PM on October 9 [1 favorite]


Mjøsa Tower, Brumunddal, Norway: "Eco-friendly, fast to build and surprisingly safe, a new generation of wooden skyscrapers, or 'plyscrapers', is taking root across the world. At 262 feet (60m), Norway's 18-story Mjøsa Tower will be the planet's tallest all-timber structure when completed in March 2019. Designed by Voll Arkitekter, the $54 million (£42m) tower will be made from prefabricated cross-laminated timber, a sustainable material which is as strong as concrete when arranged in a certain way, and extra-speedy to assemble. The wood is also remarkably fire-resistant – in the event of a blaze, the timber chars rather than goes up in flames. Other wooden skyscrapers in the pipeline include all-timber or mostly timber towers in Berlin, Vienna and Tokyo."*
posted by kliuless at 9:30 PM on October 9 [1 favorite]


My closest Kiwi (Norwegian retail chain, despite the name) reopened this year with low-C02 concrete and massive timber construction. It doesn't look half bad either.
posted by Harald74 at 12:54 AM on October 10 [1 favorite]


Bare steel? Sure. Protected steel? Concrete reinforcing steel? Maybe not.

Big wooden beams retain their strength surprisingly well in a fire... they just char on the outside and still retain most of their structural strength. On the other hand steel / any metal rapidly loses it's strength when exposed to heat (as any metal worker for the last few thousand years would tell you)... it don't have to be melting to fail.
posted by fearfulsymmetry at 12:57 AM on October 10


Right - that's why I'm saying protected steel. You can't have a building of any notable size, much less a skyscraper, without using protected steel, and if you want to go taller than 11 stories, you have to give it a 3-hour protection rating, and the material assemblies that qualify for ratings like that are actually tested. Wood that qualifies as "heavy timber" (minimum 4x6 member as noted above in a comment) basically gets an automatic 1- or 2-hour rating. Any size wood member will eventually burn through, the char is not some infinite method of protection. As aramaic mentions, any future massive wood construction isn't going to be big pieces of wood, it's going to be little pieces glued together. We're not talking cities made of wood beams, we're talking cities made of particle board. It's already somewhat difficult to get larger wood members for large beams and stuff because the lumber industry is more geared towards managed forest harvesting (although old-growth logging obviously still happens).
posted by LionIndex at 5:42 AM on October 10 [1 favorite]


Wait, we're ignoring the "Google is going to build a city and monitor the fuck out of everyone in it" part because they wanna build with more wood? Wtf?
posted by odinsdream at 9:40 AM on October 10 [2 favorites]


we're talking cities made of particle board

I'm not sure if this is just a comment on the fact the laminated materials are glued together, but calling them "particle board" mischaracterizes them as a mishmash and not types of material with very specific grain pattern serving specific purposes. "Particle board" is the language of FUD. From The Incredible Lightness of Heavy Timber, linked in the FPP:
Glued laminated timber, called “glulam,” is a structural engineered wood product comprised of a number of layers of dimensional lumber that are bonded together with all the wood fibers parallel, using durable, moisture-resistant structural adhesives. Cross-laminated timber, or CLT, is a large-scale, prefabricated, solid-engineered wood panel that consists of several layers of kiln-dried lumber boards stacked in alternating directions, bonded with structural adhesives, and pressed to form a solid, straight, rectangular product that is dimensionally stable [emphasis added].
And if we look at other structural materials, CLT is basically analogous to carbon fiber (a bunch of layers of material with a single axis of strength, stacked in alternating directions and glued together so that the whole thing is strong and stable in multiple axes). You probably wouldn't call a Boeing 787 a flying pencil because it uses carbon composites. At least I hope you wouldn't. There's a whole range of composites consisting of some sort of glue and some sort of substrate, optimized during selection and manufacturing to meet particular design goals (stiffness, weight, repairability, and so on). Glulam and CLT are just two more composites, making use of a substrate with its own set of costs and benefits.
posted by fedward at 9:56 AM on October 10 [1 favorite]


"Wait, we're ignoring the "Google is going to build a city and monitor the fuck out of everyone in it" part because they wanna build with more wood? Wtf?"

I don't think it matters who helms this. This is already basically true of most major city areas, the era of privacy has long ended and we've been in a surveillance age for over a decade now. Soon or sooner it will become normal to be constantly surveilled and analyzed. The stuff China is starting to do is baby babble compared to what is to come. I suspect by the end of my life even my sleep and dreams will be fair game for some government/business/government-business to harvest for precious datas.
posted by GoblinHoney at 1:43 PM on October 10


Glulam beams can be quite beautiful, too. They come in a variety of types and grades only some of which are anything you'd want to look at as a finished surface, but the ones that are meant to be exposed are pretty sharp. They look kind of like butcher block. Not half bad for something that is essentially made
of scraps.
posted by Anticipation Of A New Lover's Arrival, The at 5:15 PM on October 10 [1 favorite]


the era of privacy has long ended and we've been in a surveillance age for over a decade now. Soon or sooner it will become normal to be constantly surveilled and analyzed. The stuff China is starting to do is baby babble compared to what is to come. I suspect by the end of my life even my sleep and dreams will be fair game for some government/business/government-business to harvest for precious datas.

Google's Selfish Ledger is an unsettling vision of Silicon Valley social engineering (yt ;) - "This internal video from 2016 shows a Google concept for how total data collection could reshape society... where Google helps nudge users into alignment with their goals, custom-prints personalized devices to collect more data, and even guides the behavior of entire populations to solve global problems like poverty and disease."
posted by kliuless at 10:14 PM on October 10 [1 favorite]


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