More buildings should be made of wood | Hacker News Reader

More buildings should be made of wood

economist.com

42 pointspseudolus52 comments

Can wood buildings provide good sound isolation between floors?

I've lived on the 3rd floor of a wood framed 4 story apartment building, and won't repeat that experience if I can help it -- we could hear the couple upstairs very clearly, footsteps, their dog jumping off the couch and barking out the window, late-night sex, all were easy to hear.

In contrast, I lived on the 5th floor of a 9 story concrete and steel high rise, and couldn't hear anything. I even had the upstairs neighbors ask me if I could hear their new treadmill, and I could not.

I assume that the sheer mass of the concrete floors made it so quiet -- Can a wood framed building be constructed with that same level of isolation?

FWIW, I live in a brick and concrete building and hear all the things you mentioned, sometimes not just from immediately adjacent units, but also often units two or three floors away in some cases, e.g. loud parties or drilling/hammering (the rigid structure conducts the sound around the building I think - kinda like tapping on a metal pole or rail: doesn't matter where you put your ear on the pole you still hear the noise from the tapping)

loud parties or drilling/hammering? in a wooden building (in a pretty regular US home at least) you hear people gently walking or even just coughing on the floor(s) above or below you

Wood framing is not the same as a building built of cross-laminated timber. The architect must get a few details right, but it is straightforward to meet "only able to hear neighbors when jumping off a table on to the floor". OTOH it's not much more difficult to do that with standard wood framing, but they don't usually.

They can if they purposefully add sound insulation, but it does cost a decent amount more in construction and is hard to add in after the fact. Concrete is quieter without doing anything to it but it also costs from the start.

They cannot without involving way more material. The best isolation is the mass of the floor. Try moving around the second floor of a wooden building and check if the glasses in some cupboard start to clash. If they do it is because the floor bends under your weight. The only countermeasure is to increase the mass of the floor and while a wooden wall (if planned for it) could certainly carry that weight it is difficult to obtain that mass from a wooden ceiling.

I've lived in both. In the concrete building I hear nothing. In the wood one I could only hear things that directly made contact with the floor, like people walking, chairs moving etc. I could never hear anything else. But I was slightly paranoid that I was simply the only one in the building who listened to music, had sex etc.

I have built my first wood houses since few years, European class A+, short answer is yes however less than concrete houses.

Long answer structure is from lower flat and upper is:

- fibrous plaster + finishing with it's support structure

- mineral wood 100mm think between wood beams (250mmx100mm)

- OSB panel on top of beams, 30mm

- sandwich panel composed of wood wool (20mm) and fibrous plaster (30mm)

- thin (4/5mm) wood wool panel

- laminated floor

If I walk normally I do not hear too much downstairs, otherwise well... Noise passes, far more than classic concrete + rubber coat + background and floor tiles... Also when I move I hear "casual noise" from laminated floor friction. Not much but a bit yes...

IMO sound propagation is due to the fact that wood structures are lighter and elastic than concrete so vibration passes far easier and it's hard to stop them...

Yes there are a few relatively simple things that can be done to vastly improve sound isolation in wood frame buildings. They do cost a little bit so many builders don't do them.

For isolation between rooms the walls can be built with "a hollow core", which means there are, in effect, two separate walls, each facing their respective room with almost no pieces of wood joining the two walls. It's the wood that normally is touching both walls that allows sound transmission. Secondly the "gyp rock" sheets that create the wall can be stood off from the timbers they're anchored to to further improve sound isolation.

For sound isolation between floors it's possible to lay down about four centimeters of concrete over the wood floor and this hugely improves sound isolation.

Obviously these increase costs but they do really work and probably don't increase cost by more that 5 to 10 %.

That's a lead article in The Economist. A longer article on the merits of modern wooden buildings can be found in the same issue at [1]

[1] https://www.economist.com/international/2019/01/05/efforts-t...

I CTRL+F'd for "deforestation" in the article, thinking that anyone in their right mind talking about using that much more timber would at least mention it, and was surprised not to even see it mentioned.

> When a mature tree is cut down, a new one can be planted to replace it,

Again, expert carpenters could correct me if I am wrong, but the higher quality desired wood is called "old wood" some of which is over one hundred years old. You can't just snap your fingers, plant a field of trees and expect that to be ready in time to meet a surge of demand. The stuff is already extremely hard to come by -- you ain't gonna find it on the shelf in any big box store.

The vast majority of the stuff used today is "new wood", cultivated to grow as fast as possible, so the wood is not as dense and, as a result, weaker and more susceptible to decay and instability. Not exactly what I would want my skyscraper built out of.

I am assuming the author was considering composites and manufactured wood products as well -- again, these have not been proven to be as structurally sound as old wood over time.

Then the other factor in play here is the increased demand in logging. Logging is one of the most dangerous jobs on the planet. You would technically be requiring more loggers, thus causing more logging deaths.

Not so sure this is such a good idea, but I could be wrong.

That's true that newer woods are softer, but often for structural applications special types of engineering wood products are produced from newer woods which are very strong. One example that comes to my mind is structural ply, it's really strong stuff and practically always made from soft timber.

I found a reference here (https://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr190/chapter_...) that discusses the mechanical properties of some of these fabricated structural wood products. Everything seems to be in comparison to just plain hardwood, but nothing seems to point to that it meets or exceeds the strength of hardwood. I am not convinced that any amount of glue, plastics, and pressing together other hardwoods (presumably, young woods as well) will stand up against good old fashioned old wood timber, which I simply don't think we have enough of to start building tall buildings with. If that's the case I'd rather be on the top floor of a steel building.

They’re only going to design the building to be strong enough to withstand the loads it needs to bear, plus a standard safety factor. If they use a stronger material, they’ll use less of it so that the resulting strength is the same.

I can understand being skeptical of decay, fire resistance, sound deafening, or other factors like that, but being worried about the strength makes no sense.

That's also only one tiny aspect to logging. Loss of biodiversity, soil erosion, micro-climatic shifts, the impact on streams, all can be devastating in isolation, let alone together. Saying that you can plant new trees to replace old ones is a 1950s era lame-ass response to the issue, it is not suitable, let alone intellectually serious, as a "proposed solution" in 2019.

This is certainly a concern when logging old growth forests that have never been logged before, but I'm not sure it is such a concern with managed forests. I am pretty comfortable with the idea of increasing the area allotted to managed forests in the uk, particularly if it is allowing for a reduction in CO2 emmissions from homebuilding.

I also suspect that the alternative for areas that are/could become managed forests is not for them to be left alone and undeveloped.

I believe that glue-laminated timbers (which were mentioned in the article) and plywood (which features heavily in housebuilding - at least in Vancouver) can be made from younger trees.

It is plausible that foresters would struggle to meet a surge in demand, but growth in wooden house building could be slow - particularly in resistant markets (like the UK). I also remember reading that young trees remove more CO2 from the atmosphere than mature trees, so a surge in logging and replanting (and and expansion of forestry efforts to keep up with demand) could have a benefit in fighting global warming.

I am from Austria, a nation where wood is one of the most important building materials of houses since centuries.

We have more wood than we use in the last years.

Deforestation, the work dangers of logging and responsible logging (e.g. avoiding to log whole areas which leads to erosion and destructive dirt avalanches in mountainous regions; planting and growing with a long term plan) are problems of law and personal responsibility. That beeing said in Austria this was a problem in the 70s, definitly not a problem any more. Owners of wood certainly feel some sort of responsibility for the landscape they own over here.

Although fast grown woods are indeed softer, compound materials are a good alternative and I have seen houses from the early 90s that are still rocking that new technology (like my old skies). More exotic materials like bamboo (technically not a wood but a gras) offer a very good alternative in mechanical terms (also grows quite fast).

It is up to us to build the framework in which wood can be used responsibly, with all side effects considered.

Making concrete is one of the larger CO2 contributors on the planet. Trees ARE captured carbon dioxide. Cross laminate timber is very strong. We need to give value and purpose to these materials again by choosing to live and work in them.

If they are using softwoods likes pine then it is mostly all grown on tree farms industrial style and doesn't take that long to grow. Hardwoods can and sometimes are grown on tree farms but the 60+ year harvest makes it an unattractive investment.

There is no problem making things out of faster farm grown hardwood(and not all hardwoods take a long time to grow either) but due to the fairly easy availability for natural grown hardwood, atleast around me in the US and Canada, you don't see many hardwood farms. While farm grown hardwoods might be a little less dense, it isn't anything that can't be solved by using slightly thicker pieces. And on top of that, farm grown trees are better pruned and maintained, meaning better quality controlled logs with less significant knots and crazy changes in wood grain. You will get far more consistent and reliable beams and boards from farm grown wood, especially at long lengths.

The slower grown old growth trees have slightly better figure due to thinner rings but in any application where you aren't paying a huge premium for looks, it isn't that different, and 99/100 people couldn't tell the difference.

The one object you really do need the really slow grown old shit is for musical instruments where even relatively small increases in wood density can significantly improve the tone of an instrument.

I don't think that deforestation is too much of a concern for the quantities of wood needed to construct buildings that will last 40+ years. Building construction is a fairly small user of wood compared to fuel and paper products (These are roughly 75% of wood usage).

I don't see any mention of termites. Wood is much less attractive when you live in a termite-prone area - they're hardy little buggers, they can chew through concrete to get to your timber framing, and if you don't catch them early enough your entire house needs to be rebuilt.

Ahem. First google link "There is an urban legend that says that termites can eat through concrete to get into a home." https://www.termite-control.com/termite-infested-homes/termi...

Huh, there you go. Although the third link on DuckDuckGo (http://mytermitetreatmentcosts.com/do-termites-eat-concrete/) does say:

> However, older degraded concrete is occasionally weak enough for termites to make their way through. The same has been known to be true with lime mortar which is common with brickwork. Termites have been known to make their way through the lime mortar between brickwork to get to the wood behind them.

So it's not completely impossible.

Cement/concrete is a MASSIVE contributor to global warming (8% of CO2).[1]

Steel is not far behind at 5%.[2]

I feel like we need to talk about this more. Whenever "urbanists" go on about the environmental cost of sprawl and transport, first thing I think about is all the concrete & steel their vision requires. At least we can make transport sustainable.

[1] https://www.bbc.com/news/science-environment-46455844

[2] https://www.technologyreview.com/s/611961/this-mit-spinout-c...

(I guess the Economist cites different estimates, 6% and 8% respectively, but it's in the ballpark.)

You can use timber for high-rise buildings. [1]

[1] https://archinect.com/news/article/150025665/the-world-s-tal...

Most urbanists prefer putting buildings closer together with less roads and parking lots in between over building taller.

What's your source? Most urbanists I read at least in the context of San Francisco definitely advocate building taller. Maybe not skyscrapers, but at least 4-6 stories. And the "formula" for that type of construction uses a concrete first floor.[1]

I'm not against the urbanist vision per se. I've just found that it's very "politicized" and they tend to not want to talk about CO2 impact of dense urban construction like it's some kind of attack. Like, I got downvoted a bit for my comment. Why can't we talk about this?

[1] http://archplanbaltimore.blogspot.com/2015/03/how-one-plus-f...

One floor of concrete plus five floors of wood is a common pattern, but it isn't necessary. You can easily build a six story building wood frame building.

Also, a big focus of urbanists is the "missing middle"[1]. This is the idea that there is too much focus on single family houses and high-rises and too little focus on housing that is shorter, but still denser than single family houses.

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

Seems like this analysis has vastly under-appreciated wood's tendency to burn. Yes, I see they've mentioned how in one specific type of burn test "modern cross-laminated timber panels perform better in fire tests than steel ones" ... but come on, are they suggesting that any kind of wooden house is safer than a cinderblock house? Storm risk?

It's great that wood is environmentally friendly and all, but does this opinion really consider how many more humans would likely die in house fires or tornados if we all moved into wooden homes?

Vast swaths of this planets are covered in nothing but cinderblock structures, and you know another thing they don't really need to worry about? Fire departments.

They performed tests. What do you offer in your comment outside of "common knowledge". I'm not necessarily saying that you are wrong, but other than hearsay you didn't offer anything.

What kind of test is going to burn a cinderblock?

A test on the capabilities of chlorine truflourude?

https://blogs.sciencemag.org/pipeline/archives/2008/02/26/sa...

Like all things, it depends. In North America, the vast majority of houses are wood frame. The incidence of deadly house fire remains rare. If you build to code, wood frame houses can be quite safe. As for storm risk, there is a lot you can do to strengthen a wooden house against hurricanes. Cinder block houses lose their roofs just as easily as a wooden house if it is not properly anchored. There are also a lot of places where hurricanes just aren't an issue. Finally, wood generally fares better in an earthquake as it is naturally flexible whereas cinder block houses most assuredly are not.

Over hundreds of years of proximity to nearly limitless natural lumber, North Americans have evolved a highly complex network of water mains, smoke detectors, fire hydrants, and fire fighters to quickly come and put out the fires that inevitably happen before everyone burns because we build nearly everything out of flammable, cheap wood!

Imagine how much money and effort we could save if we build shit of of something that doesn't burn!

What usually burns is inside the house, not house itself. And once a house burns, it must be usually demolished as a whole, because its not stable anymore (concrete doesn't likes fire). In wood house you can teoretically 'cut away' the burned part and build it new ;)

>>concrete doesn't likes fire

I guess depends on the intensity and how long it lasts. Pretty sure a concrete home can survive your sofa burning. A wooden house, it's toast.

I've found small fire test, its not very scientific, but shows what I was talking about:

https://www.youtube.com/watch?v=G-J86Ka9MkQ

To correct myself, its the mortar that doesn't likes the fire much more than pure concrete, therefore brick wall has to be usually demolished after fire. But yes, everything depends on intensity of the fire, but I would never say that (properly built) wood house burns easier or faster than brick house, its kind of a myth. It burns differently with different result, and different kind of damages. Where, in the wood house the damages can be _usually_ fixed easier as in brick house.

Cross Laminated Timber is pretty fire resistant - chars on the outside protecting the inner wood

http://www.greenspec.co.uk/building-design/crosslam-timber-f...

I have built since few year my first wood house (Euroclass A+) and have had very limited "long-term" experience of wood structures for small "garden-like" construction, in summary: they are damn good in terms of thermal isolation, fire resistance (yes, wood burn, but structure sustain heat more than concrete!), and maintainability (especially to change something inside, if wood is properly designed) however we should copy Japanese way of wood fitting to avoid metal fasteners (screws etc) because after years they tend to loose simply due to internal forces in the wood structure due to thermal dilatation etc.

Also I do not really now how long steam brakes towels can last, they are plastic and plastic normally do not last longer... Formally they are guaranteed 10 years. If we have designed implants properly they can be changed with a long but not extreme work however...

Another point is fragility in general: to have proper insulation, at least in EU but I assume also in the rest of the world, we use "VMC" (forced ventilation with air-air heat exchange) and while they are essentially brushless motors running calm and slowly they have filters, humidity regulators (that are essentially "heat pumps/fridge like machines) etc and again I do not know how much they can last in years.

With a broken ventilation living it's hard, I experienced it very well since I have start inhabit my house before it's completion and I have to keep windows opened a bit or I literally suffocate inside in around 12 hours... And the resulting "closed smell" was really high... Probably that's the very same thing for modern concrete construction but that's is... Without some machines and electricity it became really hard to live inside...

BTW I'm happy and I note to some likely to downvote in these arguments: this imply little buildings like two/three floor maximum. We can build taller building in X-Lam but they are more experiment than reality. So draw your conclusion. The population model for modern wood houses it a Riviera model, not a skyscrapers town.

Previous discussion on making more wooden buildings: https://news.ycombinator.com/item?id=18174491

What it's probably gonna come down to is, can we make it cheaper than other methods? Will someone make enough money to really push modern wood composite prefab structures? Because let's face it, the construction industry doesn't give a crap about sustainability.

Wood is good. Straw is even better.

Fire and earthquake resistance are two big advantages straw building has over brick, concrete and metal.

Have a look at the wikipedia article [0] for a short intro.

[0] https://en.wikipedia.org/wiki/Straw-bale_construction#Proble...

This company seems to be doing wooden bricks (or legos): https://www.aaltohaitek.fi/frontpage

How about just building less houses? Even China has overproduction of houses. All comes down to our economic paradigm where we need to produce infinitly otherwise we colapse

There are an awful lot of unforested areas which could be planted with trees. I'm surprised none of the green initiatives are about planting large quantities of trees. Trees remove CO2 from the air, sequester it in wood, and provide lumber for building.

I'm a bit leery of wood skyscrapers, however. What happens when they burn?

Wood tends to burn quite slowly and retains structural strength at high temperatures that would compromise steel.

The tallest wooden building allowed is only five stories. Wood framed buildings higher than that need special approval.

http://www.woodworks.org/experttip/what-is-the-tallest-wood-...

Despite the international in it's name IBC is mainly a US related building code

As youngtaff points out, this is not true internationally...

London, UK, 10 storeys: http://waughthistleton.com/dalston-works/

Vancouver, Canada, 18 storeys: https://www.thinkwood.com/our-projects/brock-commons-tallwoo...

And then there are hybrid wood/steel structures, with a Japanese company planning a 70 Story tower:

https://www.bbc.co.uk/news/technology-42839463

I'm sure Paradise, CA would disagree. There's no one construction material to rule them all, it should be chosen based on the local environment/situation.

A wood construction doesn't catch fire more easily than other building materials if done properly. In fact once caught fire wood is much more predictable than other materials.

> In fact once caught fire wood is much more predictable than other materials.

Uh, once caught fire, the structure is compromised and almost always lost. Success? (lol)

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