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At 18 Stories, Mjøsa Tower Is World’s Tallest Wooden Building (cision.com)
206 points by prostoalex 27 days ago | hide | past | web | favorite | 154 comments

There is also the HoHo building („Holzhochhaus“, lit. wood high house) in Vienna, which is a wooden high-rise with 24 stories and 84 m [0]. They just added an antenna to the Mjøsa Tower to break the record. (Boys and their towers…)

[0] https://de.m.wikipedia.org/wiki/HoHo_Wien

A thousand words of German, including a section on its impact on the skyline, but the only image is the HoHo logo? I know I could edit it myself, but this just seems strange for any notable building.

This is very common for German Wikipedia.

Once I had the idea for a project (never completed) to analyze the differences in pictures accompanying articles across Wikipedia's languages. The results were about what you might expect. For their respective articles on "Food", you'll find:

- English: a photograph of vegetables, meat, bread, beans, and milk

- Japanese: a room full of tuna at a large fish market, white rice, and water

- Russian: potatoes, onions, spices

- Italian: a 17th century painting of some food

- Esperanto: the cover of an Esperanto book about food

- German: bar charts tracking food prices (and no pictures of any actual food)

It's interesting how Wikipedia makes it easy to jump between languages, yet each language's maintains its own identity and conventions. I've heard people propose to just start copying photographs from English Wikipedia into others (which tend to have far fewer pictures), and editors for those languages asking people to please stop.

The same applies to Wiktionaries - compared to English, the French Wiktionary is elegantly and spaciously structured, the German version telegraphic and dense on information.

That's pretty interesting. The English approach (or the Japanese, or Russian) seems objectively better to me. I guess for something like "food" it can lead to a mild case of cultural imperialism, but having a picture of the thing is generally better than not having a picture, and AFAIK Wikipedia explicitly makes it easy to share media between the different language wikis.

You'd need to provide an image with a copyright status appropriate for Wikipedia, which might not be trivial in some cases.


According to that article, HoHo is only 75 percent wood and has a concrete core for the elevators. Still, pretty good.

Wikipedia has a list of tallest wooden buildings, very few of which are actually complete: https://en.wikipedia.org/wiki/List_of_tallest_wooden_buildin...

I recently read about the one in Tokyo which is supposed to be 350 meters tall for a forestry company's 350-year (!) anniversary. The article claims it will be 90% wood, 10% steel: https://e360.yale.edu/digest/tokyo-plans-to-build-1-150-foot...

According to the original article, Mjøsa Tower also makes use of concrete, though a % isn't given.

But not for structural support, it is to provide mass damping. They could have used lead weights instead.

This Swiss company makes all-wood houses: meaning no insulation, they just make the solid wood walls thick enough to pass insulation codes without requiring foam or fiberglass. Also no metal fasteners.


> "In fact, wood is a fireproof material despite the commonly held belief that it isn’t."

What? I hold this belief that isn't. I understood the point about keeping its structure well while burning, but it doesn't make it "fireproof"!

Eh, I think this is a jargon issue.

Wood obviously isn't fireproof. But we have regulations that say that in buildings "fireproof" just means it will last some amount of time before burning or degrading/collapsing.

Ex: if you're in an office with a wooden door in the US, go check the side of the door where the hinges are. Most will have a small metal plate indicating that they're rated for some amount of time for fires.

It will look like this: https://www.google.com/search?biw=1903&bih=898&tbm=isch&sa=1...:

This is what a forest looks like after a fire: https://commons.wikimedia.org/wiki/File:Forest_fire_aftermat... .

Note that the trees are all still there. Wood is surprisingly difficult to burn, and if it does, it will do so very predictably, slowly, with relatively low temperatures, while maintaining structural integrity.

This video makes the difference very clear: https://www.youtube.com/watch?v=G-J86Ka9MkQ . It's not that wood can't burn, it's that it won't burn significantly.

How do the wooden buildings fare in towns consumed by forest fires? What about the steel, concrete and masonry buildings?

I wager that if we built forest like structures out of steel and concrete they'd be far more fire resistant than natural, wooden, forests even if the amount of fuel at ground and canopy level was kept constant.

This whole wooden building thing is great for a variety of reasons. That doesn't mean it's not inferior to steel/concrete when it comes to resisting a major fire. Just because it's inferior doesn't mean it can't still be "good enough". Trying to claim that a wooden structure has superior fire resistance to a steel/concrete/masonry structure is an exercise in mental gymnastics.

Well, the typical wooden buildings you're probably thinking about (ie, suburban housing) would be terrible and burn completely. If you take a look at their construction, they use relatively thin pieces of wood both for structure and walls.

CLT or Mass Timber buildings are very different, there's basically a crapload of wood and it is very dense, so dense it can't burn well because oxygen can't get to it very well.

It is essentially the difference between trying to burn kindling vs a single large log.

>I wager that if we built forest like structures out of steel and concrete they'd be far more fire resistant than natural, wooden, forests even if the amount of fuel at ground and canopy level was kept constant.

Depends on the type of wood. There are some trees like Aspen that are natural fire barriers because they don't burn well. Unfortunately they're not worth much, so in places like BC that have a big logging industry they spray them with Round Up after the major forest fires. It's one of the real reasons that fires here have become so massive lately.

There was an article on HN recently, that the most fire-catching part of most California buildings is their shingle roof, regardless of inner construction.

And old fireman said that Steel will burn like crazy. Tree probably burns slower. Concrete also "burns" and will change characteristics (become weaker) when exposed to high temperatures. I wouln't like to be in a burning building, but a wooden building would probably be least dangerous !?

Somebody was just telling me that oxyacetylene torches cut steel by burning it - not melting. That's why they won't cut stainless steel, they can't burn it (oxidize it).

Plasma, cutters, on the other hand, cut by melting.

Oxy/fuel cutting is more like rapid oxidation than burning. The reaction is not self sustaining without fucktons of oxygen (you can burn basically anything if there's enough oxygen present). The oxygen stream helps blow away partially oxidized steel. It only works with steel because of the specific combination of metals other than iron in steel. It won't work on cast iron or stainless (though you can certainly melt them).

Plasma cutting liquefies the metal with electrical current then blows away the molten metal with air.

Take an oxy/fuel torch to a piece of wood and you will quickly have a self sustaining reaction even once the extra oxygen supply (torch) is removed.

It doesn’t make mention but I wonder if to reach 18 storeys this is chemically, heat and compression treated wood? Also, no mention on how they’d keep insects at bay, given the structural criticality of this wood.

Never the less, very exciting to see wood so prevalent in new construction.

There was this[1] recent discussion on new wood frame midrises being very prevalent.


It's all engineered lumber. "This high-rise is being built using glulam, CLT, and Metsä Wood’s Kerto® LVL (laminated veneer lumber)"

glulam = glued laminated timber AKA pieces of regular timber stacked & glued together CLT = cross-laminated timber AKA glulam but instead of stacking the lumber, you lay it out in perpendicular layers and glue it together LVL = laminated veneer lumber is like the above, but made like plywood out of wood bits instead of solid lumber, with a hardwood veneer on the outside

The wood is also treated to be fire, moisture, and insect resistant

Given one of the things that wooden buildings inspire is a "Hey, we CAN build big buildings in a green manner", how do all the things you mention impact that?

It sounds like gluing, treating etc. etc. would really impact the "greenness" of this building

I think the green-ness relates more to the fact that growing timber captures carbon dioxide, while producing steel and concrete emit carbon dioxide. The production of the glue, and the processes to glue the timber together certainly emit CO2, but nothing near the emissions of a steel foundry.

Cement production emits 5% all man made CO2 emissions.

On top of the other replies, you should keep in mind that being more green than producing concrete is pretty easy.

That's true, but here's a thought: Using engineered wood products potentially allows undesirable or unconventional wood sources to become useful building materials, rather than having to source old growth timber for larger beams/columns. There could be some environmental benefits associated with that.

I agree with your comment but I just need to point out that beam/column timber is not old growth wood, it's usually just from normal commercial plantations.

You're right for typical studs, joints, posts, etc.

However, I was thinking that for a highrise timber building, you might need way larger column cross sections than what we're used to seeing (24"x24" - 36"x36" or larger). The typical wood frame construction method of using a ton of load bearing sheathed stud walls scattered throughout doesn't work with these taller types of buildings. You start to see post and beam/panel type framing, which means higher compressive loads, which means larger member sizes.The spruce/pine/fir trees slated for harvesting softwood lumber here in Canada don't seem to reach that size. Hence, you probably need engineered wood products. As a bonus, you also get better and more consistent mechanical properties.

Old growth wood is not suitable

It does, but the material is still carbon-negative, the article says.

In any case, anything is better than concrete.

What’s the problem with concrete? Edit-answered above, concrete produces carbon while wood stores it.

So many people have seemingly given up on wood for strength and durability. As an engine mechanic by trade, some of the strongest equipment in my shop is wooden.

- My diagnostics table can support a load of 2000lbs. You could park a golf cart on it.

- my Stronghold work bench will handle up to 8000lbs of load. You could park an F250 on it.

both of these are maple top/butcher block.

There's a reason brick doesn't get taller than 20 stories - the walls at the base get thicker, the taller it gets. At 20 stories you're basically building a pedestal on the bottom, to hold up the top. At that point you just get a larger pedestal on the bottom, and no more usable space going taller.

I wonder what the limit is for wood?

If you're ever in Chicago, check out the Monadnock Building. It's the tallest load bearing brick skyscraper (16 stories) and the foundation goes underneath the sidewalk.

Brick on the outside; braced on the inside. From the Wikipedia article:

"the masonry walls were braced with an interior frame of cast and wrought iron"

I'm excited for more wooden buildings, but the claim that "Compared to cast-in-situ concrete, wood makes it possible for construction time to be slashed by half" seems very optimistic.

There's a building boom going on around my office. The steel and concrete office tower next door is by far "sprouting" the fast. On the other side is a residential tower where half of the building is a 20+ floor concrete tower, and the other half is a 5-floor wood frame structure.

The concrete tower is going up faster, despite this being the same construction project. Perhaps what I'm missing is that a CLT build is more similar to steel construction than a wood frame building. Perhaps a real civil engineer can weigh in...

I used to work in Construction Management on the structural concrete side, so I can weigh in (a little) on possible reasons why the CIP (cast in place) tower seems to be going up faster. Generally, CIP vertical structures have minimal changes from level to level, so as the building goes up, the construction crew (generally Carpenters, Rebar/PT laying crew, and concrete placers/finishers) will become much more efficient at their work. Also, there will be minimal 'fine' work on creating floor plans on a CIP deck, it will be a primarily flat surface, excepting stub walls (for steel stud walls), utility penetrations, possibly other stubbed elements for vertical shafts and etc., elevation cuts, and sloping. The structural concrete sequencing is such that the bare core structural body is formed first, and other trades will populate it to create the finished product later on. With wood framing, I am not too familiar with the process, but I believe many of the stud walls have structural properties, and in general much more of the finished 'shape' of the floor will be done in the wood framing process from level to level.

Seattle is just now allowing wood construction in high rise buildings. Previously they were an early adopter in mid-rise buildings which is why you see a lot of apartment buildings with exactly 6 stories around (1 concrete ground, 5 wood as allowed by the building code).


In South lake Union Seattle also has a lot of midrise because of height restrictions around the space Needle. The needle is not actually that tall, the city is afraid that rampant real estate developers could completely hide it in the skyline.

Actually I think it's because of the seaplane flight path https://www.seattle.gov/Documents/Departments/OPCD/OngoingIn...

I think the claim is plausible. If you've ever watched Grand Designs, a lot of the houses (especially the cheaper or less traditional ones) use prefab pieces and are incredibly fast compared to traditional timber frames with poured concrete.

In the last few seasons, in particular, a bunch of the houses use pre-built wall (and even floor) "cassettes", also called closed-panel frames, that come with everything from the factory -- not just structural framing, but layers of insulation, breather membrane, vapor barrier, etc., complete with inside-facing gypsum drywall -- and simply lock together.

There are also lots of examples of custom off-site-engineered steel or wood pieces that are CNC-machined (almost always shipped from Germany or Switzerland), and also very fast to install, partly because they can machine them to a high precision. At the construction site, it's just assembly.

I'm not a civil engineer, but I do know that a CLT (cross-laminated timber) building can get built faster because many parts are pre-fabricated panels. The University of British Columbia (UBC) built a 18-story wooden building (which is shorter at 54 metres), and it was built relatively fast:


This building has two concrete cores (elevator/stair shafts) for lateral resistance that were built ahead of time, and then the wood gravity system came later, So it kinda took more time than normal.

Another fun fact - alot of that nice looking wood had to be covered up with drywall for fire code compliance.

I got to watch that building be constructed during my masters, it was pretty amazing to watch how quickly it was constructed.

Fun fact, UBC has like 3 18-19 story dorms with million dollar views of the entire surrounding area.

Concrete setting times depend on ambient temperature. Too cold and concrete takes longer to achieve the necessary strength to start the next level. Admixtures and other techniques can improve this.

So the claim for taking less time than a _concrete_ building is plausible for this location (I assume it's pretty cold compared with other climates). However like you mentioned, a _steel framed_ building would be similar in build time, since the elements can be hoisted and joined in the same way as a CLT building.

But that also depends what your slabs are. Most steel framed buildings use concrete slabs, which need to be poured and set, but with high early strength concrete and propping, this takes less time than a conventionally formed concrete building.

Concrete buildings can go up really fast, I've seen 5-6 day cycles on jobs. It depends on the complexity of the structure and again the ambient temperature (among other things). So yes concrete can go up faster than CLT as you noted.

As an interesting side note, the article mentions that the top floors of this CLT building use concrete for mass to limit swaying.

That article is from August 2017. The latest one I can find on the tower is from September 2018 but it appears to be nearly complete (target completion data is March 2019).

[1] https://archinect.com/news/article/150084833/the-world-s-tal...

In my opinion, it looks really dull and plain. It's kind of sad that they would demo such a technology with a so bad-looking tower.

The picture in the article is a computer generated rendering, the real building looks better.

Although if you don't like the "Scandinavian" school of design. You are probably not going to like it anyway.

Here is a page with some photographs and more details: https://www.artwave.it/ecowave/ecoarchitecture/eco-tecnologi....

After seeing what this winter's repeated freeze/thaw cycles have been doing to my city, I'm rethinking the idea that wood is less durable, too.

Winters are always tough, but climate change seems to be exacerbating it. Where, once upon a time, it used to get cold and stay cold, now the temperature bounces back and forth across the freezing point, and, from what I can tell, it's taking a serious toll. The streets are increasingly a giant mess of potholes and spalling, the sidewalks are a mess, and even the buildings are starting to fall apart. Yesterday I heard about a person in my neighborhood being hit in the head by a falling chunk of masonry.

How does it do with acoustic isolation? Do you hear every footstep above you?

Exactly. I used to live in a low rise apartment building which used modern wood construction. Not only did I hear everything above me, but the shock waves (from foot strikes) would also travel thru the structure, so you could feel everything as well.

The Sheffield Winter Garden is a marvel of large scale wood based structural engineering, ironically enough in the heart of the UKs steel city:


This article is from 2017, and according to it, the building should be just about completed today.

Any news on how it is going?

Drove past it two weeks ago, looks like it's closed to finished. It felt so out of place. Anyone that knows Brumunddal knows that there's not a lot of tall buildings around. I guess the people on top will get an amazing view though.

There aren't even many 18 stories tall buildings in Oslo.

This is really impressive, but what's the real lifetime is going to be?

Gol Stave Church is an ~800 years old wooden structure [1]. Most of the exterior paneling have been replaced, but the interior structure is original. And there are plenty of wooden exteriors in Norwegian houses that are 100-200+ years despite the climate.

I grew up in one that was about 100 years old and where the exterior was all timber covered with plank. Originally there was sawdust added as insulation, but that was replaced at some point in the 1980's due to the fire hazard.

Of course this building is all specially treated wood, and the structure is under a lot more strain, so it's not guaranteed that it translates well, but wood that's treated properly can last a long time.

[1] https://en.wikipedia.org/wiki/Gol_Stave_Church

Sorry, but you can't compare a multistory building where people live with an old church.

How about a 500-year old multistory building still used as a house? https://en.wikipedia.org/wiki/Begijnhof,_Amsterdam .

Granted, it's only 6 stories, but I think we can forgive that, given that it's 500 years old.

That is really impressive. However, this is an exception, not the rule and I've seen a number of old wooden houses in really, really bad shape when I lived in Sacramento. Even after 50 or so years. Of course, they have termite problem in California, that doesn't happen in other parts of the world as much.

You can to an extent, because the point is that the wood retains a sufficient carrying capacity for centuries to not fall down. I'm not saying a multistory building will survive for 800 years without maintenance, but that the carrying internal structure of a church like that can survive for 800 years is a pretty good indicator that it can survive for a long time.

Well, the wood isn't going to rot if treated and kept dry enough. What's more worrying is how (if) the wood will warp over time, with expansion / contraction due to temperature differences, etc. And how that compares with concrete.

Cross-laminated wood is apparently very stable.

People also ask about fire resistance, but the outermost layer gets charred which then protects the inner for quite some time, compared to traditional steel beams where the heat makes the steel soft. So even though the steel doesn't burn, it needs special fire protection to stay stable for long enough for people to evacuate.

Does anyone know about the lifetime of the usual (non-wood) tall buildings, skyscrapers? I always wondered..will they just fall down one day..or what?

The issue isn't that they fall, but they become outdated much earlier for other reasons. For example, materials (asbestos). Or that they don't comply with newer fire safety regulations. Or that the old design no longer accomodates modern working conditions, etc.

when i see that pressed/glued bamboo kitchenware, i wonder when the bamboo is going to take over the world. Being basically just a crazy fast growing weed grass and thus cheap and abundant, bamboo tensile strength is higher than that of steel, it is harder than oak yet lighter, bamboo cables only increase strength when getting wet :


>bamboo tensile strength is higher than that of steel

What? Tensile strength of steel is like 400-1200MPa, Bamboo is < 100 MPa.

strictly speaking you're right. My statement is more along those lines:


"Although, the tensile strength of steel is 2.5-3.0 times higher than bamboo and the specific gravity 6-8 times that of bamboo; but by counting their tensile strength/unit weight (bamboo vs steel), the tensile strength of bamboo is 3-4 times that of steel."

As yes, wood has some pretty impressive properties if you normalise by density. But that also means you need bulk to match other materials.

Years again I was on a tour of the Johnson space center in Houston, home of the astronaut training facility.

As we were looking at a return capsule I noticed that the interior surfaces were finished with some kind of wood, which struck me as odd, and I asked if it was for aesthetics.

The astronaut standing near me explained that wood had the best trade-off of many criteria including weight and durability, and the goal was not to look like an 80s station wagon dashboard.

But why build 18 stories building at all, in a pretty small town (it looks like)?

Partly because they can; it's very much partly a demonstration of the technology. Partly because it means not having to let the town spread out and take over surrounding farmland and wilderness when you can build up.

Also plentiful access to raw materials. Lots of timber production around Brumunddal.

Is the timber that is used local?

Building tall is the best way to keep the town small.

It's also the most environmental-friendly thing to do.

> When you have a building made of steel and concrete, the steel melts and the building collapses,” says Erik Tveit, Project Manager at HENT AS, the general contractor for the site.


If I want to build a robust wooden house, where should I go ? What kind of resources should I look for ? Any recommendation ?

If you're building a house no more than 3 stories high then regular wood construction with 2x4s spaced every 16 inches is plenty robust, unless you expect to be hit by floods or hurricanes. And if you do expect hurricanes then wood isn't a good option regardless of construction.

> 2x4s spaced every 16 inches is plenty robust

The current recommendation is 2x6 exterior framing with 24 inch spacing. This results in a durable and energy efficient home.


Haven't the building code changes in Florida since (I think) Hurricane Andrew advanced the limits of what stick-build, platform-framed structures can survive?

I know metal roof tiedowns ("hurricane clips") were created to solve the issue of roofs being peeled off wholesale by high winds catching them under the eaves and lifting.

The codes in question are more about requiring builders to do a better job fastening the wood to the other pieces of wood than they are about the strength of the roof itself.

Building codes in hurricane prone areas basically require you use all manner of various stamped steel plates and hangers to hold things together to compensate for the fact that nails tend to rip out of things if you pull in the right direction.

One answer to the robust question is to build an eco house, perhaps partly underground. You want sustainability? Aim for more than structural integrity, but how it related to its environment and social structure.

Here's a clickbaity-but-useful-article showing some different designs, and the Welsh Preseli community is particularly interesting for there sharing of designs. A quick google will find you lots of resources for all budgets.


>If I want to build a robust wooden house, where should I go

Your local lumber yard. Wood is cheap. The easiest way to make a robust structure out of wood is to just use more material than you normally would.

How robust? Search for "timber framing", there are schools and builders who specialize in it. And of course thousands of hours of YouTube like with any craft.

Wood is terrible for multi-tenant buildings. Ever hear your neighbor walking around in a concrete/steel building?

It's also really ugly.

No: you find it ugly, but that's just your opinion.


If there's no such thing as objective beauty measures, then please explain to me why European cities with predominantly traditional architecture have vastly higher numbers of tourists than European cities with predominantly modern architecture. You can't argue it's due to lack of history, or culture, or any other measure, as Europe is vast and diverse, and you can control for all of those other variables.

There's weirdos who actually enjoy Brutalist architecture. But the vast majority of us clearly do not. That by itself should give you a hint that there is such a thing as "more beautiful" and "less beautiful".

I personally find most historical buildings unattractive... but I still enjoy visiting historical cities because of the culture and history they’ve built up over the years.

I also find a few brutalist buildings attractive. My soft spot for brutalism probably comes because as a kid I played on a brutalist playground, so it kind of just feels like the “natural order” of things to me, whereas someone who grew up around a different set of architecture might feel more at home in their “natural habitat.”

I just said that there ARE people who enjoy brutalist architecture.

Just not the majority of us. If it were otherwise, Moldova would be overflowing with tourists. As it stands, it's by far the least visited country on the planet. Sure, there are other reasons for that as well (political, cultural, economic), but to fight me on this point is ludicrous, in my opinion.

Do the vast majority of people go to Moscow to visit the Kremlin, or do they go to visit a random Brutalist neighbourhood. You and I both know that most tourists just don't do that. Why? Because they find it unattractive.

Therefore, people do make value judgements about beauty, and when a vast number of them say something is beautiful, and something else is ugly, I'd say there's objective data to be extracted from that.

Beauty is in the eye of the beer holder.

If that was true then it wouldn't matter what buildings look like at all.

Beer includes free goggles.

"Using wood means greater fire safety"

Edit: Outside of how ridiculous this statement is, how does one bring a charred wooden high-rise back up to code?!

There was an article some time back about fire ladders and how wooden ones will still be structurally sound after getting quite burnt, while metal ones can lose their integrity well below temperatures where the metal would actually melt.

I think it was in relation to the San Francisco fire department.

The SF fire department uses wood ladders because they are non conductive, vs aluminum. They operate in an area with a lot of aerial AC power lines.

And worse, 600 VDC trolley lines, which are closer to the ground than uninsulated distribution feeders. Unlike power lines, trolley wire covers a sizable fraction of street area.[1] Trying to raise even a 20 foot metal ladder is dangerous.

[1] https://www.munidiaries.com/wp-content/uploads/2015/11/wires...

Vancouver has a lot of electric trolley buses, makes me wonder what the fire department has standardized on...

yup. that's the one

The I-beams used in modern highrise construction are a world different from lightweight aluminum extrusions used in ladders.

Aluminum is one of the butter metals.

I beams are quite safe if the fire retardant remains on (a major cause of the WTC collapse was the fire retardant getting blown off by the impact).

Trusses on the other hand are quite dangerous in a fire.


A truss structure is a design not a material though, are you saying all truss designs are dangerous in a fire regardless of material?

An I beam is also a design not a material, if you want to be pedantic. You can buy aluminum ones.

That's fair, but I know of no aluminum I-beams used in modern highrise construction which is the context of my sentence.

Truss roofs are made from steel of various shapes, even I-beams, and wood. I'm only asking for clarification if all truss designs regardless of material are problematic in a fire.

That was compared to aluminum(!!!!) ladders. Aluminum loses strength far more rapidly when heated compared to steel.

If you're the fire department, and you're moving them around regularly (as opposed to a fixed installation), the weight advantage of aluminum over steel is probably compelling. Wooden ladders are heavier than aluminum, which is part of why you no longer see them for sale at most stores, but they're still lighter than steel.

SFFD uses wooden ladders due to overhead power lines, predominantly.

For the same reason you won't be starting your bonfire with the big logs. It has a huge thermal mass and it takes a lot of external energy to make the fire self-sufficient.

It's also easier to repair, as you can just replace the damaged wood. With concrete that's not so easy, and in some cases it can be hard to even gauge how damaged concrete is from fire damage.

According to this study, it does not compare too bad: https://www.firechief.com/2017/03/14/are-wood-frame-high-ris...

Thanks, this is a good summary of something I wasn't paying attention to. It contains an interesting point:

The standard of workmanship (particularly in the installation of plasterboard or sheetrock) is a critical component to the necessary fire resistance

steel gets floppy before it gets melty. Wood stays rigid as it burns until it snaps.

Many factors when thinking about which is better.

Build the structure with steel pipe. Fill it with water. The temperature can not exceed the boiling point of water until all of the water has been boiled away.

Steam expands, so you're going to have some nasty pipe explosions in there. Also you'd need a way to stop the water corroding it from the inside.

No, the steam comes out. The water won't boil if it is contained under pressure, and it must boil in order to keep the temperature down.

Dirty water and a bad choice of steel will lead to corrosion, so don't use those. Purify the water and/or use a different type of steel.

Went to a talk about this (among other things). Short answer: They size the structural members making an allowance on depth from the surface for char (zero strength) and a further depth of affected material assumed to be weakened. The unaffected wood inside is what supports the structure.

For a dramatic demonstration of how shallow a fire actually penetrates wood over a short period of time and how well it insulates, see here:


(Promotional, but informative nonetheless)

Yea, I went looking for the same thing. I find it misleading to claim that steel melts in high rise fires and collapses (only three times in history) but wood chars and becomes fire resistant (at same temperature to melt steel??).

I would never choose to live or work in a multi-Tennant hi-rise due to fire risk.

You don’t have to get anywhere near melting temp to weaken the beam strength of steel.

From the internet: Average building fires reach temperatures of 700 to 1000°C. Steel weakens dramatically as its temperature climbs above 230°C, retaining only 10 percent of its strength at 750°C. Wood generally does not ignite until it reaches 250°C. Once it catches fire, wood develops a protective insulating char layer. After 30 minutes a large wooden beam will have lost around 25 percent of its strength in a 750°C fire and retain structural integrity – a steel beam will have lost 90 percent strength and will have failed.

I'm speculating, but steel takes up less space for the same strength, so you can use that extra space for fireproofing/insulation. How would this affect the calculus?

Absolutely! Its a matter of dimensions, for wood we simply oversize a few centimeters to burn through to make sure it holds long enough to get out of the building. I assume this indeed takes more space than a fire insulated steel beam. The achievement here is the Norsk got over the medieval fear of burning houses and can now use their loved local wood to tackle urban densification challenges!

Wood can be very very low carbon compared to concrete as a building material because the wood itself is a carbon sink.

But what is actually burning in a steel and concrete structure? Drywall and carpet?

Some guesses: furniture, bedding, appliances, clothes, papers, trim, flooring, paint, etc.

Usually nothing, because this pretty much doesn't happen. It is nearly correct to say that steel buildings never burn down. The last exception to this rule involved luggage, seats, and lots of jet fuel.

What is burnt may never burn. See Shou Sugi Ban (焼杉板).

Charcoal? Coke?

Production of charcoal and coke both depend on not fully burning the wood or coal, by constraining the oxygen supply, but by heating/baking it to reduce the water content and volatiles. Older processes burn more of the material, in part to help produce the heat, while newer processes try to fuel it mostly of the off-gassing.

But the comment above is referring to a specific treatment of wood by charring the outer layer to make it act as a fire retardant.

My understanding of Shou Sugi Ban is basically to create a charcoal layer on the wood, so its unclear to me how that would prevent it burning, as charcoal is designed to burn. At best I can see it increasing the ignition temperature.

It's not fully charcoal (fully carbonized). Wood is mostly two compounds: cellulose and lignin. They undergo thermal decomposition at different temperatures. By partially burning the exterior, you decompose the cellulose, and when you attempt to set it on fire again, it's harder to light, because you no longer have the cellulose decomposition to provide fuel, but have to get to a higher temperature for the lignin to decompose.

It's charred, but not charcoal. And yes, mostly it just makes the ignition temperature go up. But that's half the battle for fireproofing. You're mostly not trying to stop it from ever burning, but giving people enough time to evacuate, or the firefighters to put it out with water.

Same old ugly Bauhaus architecture. Showcasing a beautiful building would do a lot more to promote innovative construction methods.

I don't understand how this is described as "green"? Maybe someone can explain this simply, without emotional bias.

Concrete production creates large amounts of CO2. Wood production does not.

Also steel production procduces a lot of CO2. So much in fact that some steelworks are switching to hydrogen instead of coalbased for its steel.

It would be nice to see some numbers. It might be true that this building created less CO2 but if it cost a lot more than concrete then it may be better to just build concrete and use the money you saved to remove CO2 some other way

Ok so below were some comments.

TL;DR: carbon sink, pulp wood rather than old growth, trees get replanted.

I think that is all fine and dandy, but I personally would prefer an article simply describing the building. I don't think it's necessary to go the "this is green" or "better than concrete" route. For me good is good, that's it. Don't need to play towards a debate.

In most of the world, people consider climate change scientifically proven. There isn't a debate. In Norway, the building is featured as "green" because that is desirable in a world where we want to limit CO2 emissions and other environmental harm

You missed what I was saying. Using wood is highly dependent on region.

In other places, the greenest building is the one that is already standing. Even if it may be made from concrete.

Concrete production actually produces a surprising amount of co2 globally it is the source of 5% of all co2.

There's work underway to make concrete carbon negative "greener" by mixing it in a sealed container and adding other chemicals to it to bind the CO2 and added carbon as a solid component of the finished concrete. I can't recall if it's the lime or Portland cement step of the process.

What debate?

A generalising debate about which construction techniques are "better".

Every place has it's own most adequate materials. In Norway it may be wood, in Japan it may be bamboo, but in many places it is concrete or some upgrade thereof.

I didn't like that the article is basically an advert.

"In fact, wood is a fireproof material despite the commonly held belief that it isn’t."

I stopped reading at that sentence. They went too far.

I can believe that wooden construction techniques have improved over the past however so thousands of years. But I can't bring myself to believe that it is environmentally sustainable.

In countries like Norway, the timber companies replant trees. In addition, the growing trees suck up more carbon in comparison to the older trees. You think that mining is preferable to this practically infinite renewable resource?

It is renewable, but trees take time to grow, and there's only so much space available that's useful for growing those trees. I'm not saying you shouldn't build things out of wood, but the question is how much supply is really reasonably available?

Wood for construction (and paper) is harvested from fast-growing industrial pine plantations. Building with old growth wood is inefficient even if it wasn't socially unacceptable. The demand for that stuff is all in high-end furniture and other decorative items.

Creating building from wood act as a carbon sink, the CO2 is kept in the wood and not released to the air. So using fast growing wood produce negative Co2 output. Also because of among other things, longer growth season from climate change Norway is getting more forest, not less

How much co2 is captured in a 18 story building?

Don't know. But building from wood store co2, building from concrete produce co2. Are probably several papers on this online, and would have been nice to know where to easily check things like this

Why? Compared to concrete, wood is massively lower carbon.

I suppose we could get into the weeds of 'sustainability', in that case, unless you're proposing to stop all construction of any decent height, this is probably the best we can reasonably expect.

Various sources say that lime production for concrete creates around 1/12th of the anthroprogenic atmospheric carbon. On the other hand, wood is a temporary carbon sink until ot burns or decays.

It’s a pretty good carbon sink if you replant the trees.

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