
Wooden high-rises change city skylines as builders ditch concrete - kawera
http://www.theguardian.com/artanddesign/2015/dec/12/wood-high-rise-buildings-urban-architecture-skylines-new-york-city-oregon
======
Aqwis
Here's a video about a 14-story building like this in Norway. The video is
from last year, but it was completed just this month.

[https://www.youtube.com/watch?v=e5XsqauBCX4](https://www.youtube.com/watch?v=e5XsqauBCX4)

For those of you who understand Norwegian or are willing to use Google
Translate, there's an article about the building here[1], which also mentions
some of the same projects as the Guardian article.

[1]: [http://www.bt.no/nyheter/lokalt/Canada-sikler-pa-bergensk-
ve...](http://www.bt.no/nyheter/lokalt/Canada-sikler-pa-bergensk-
verdensrekord-3498825.html)

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vlehto
I'm bit worried with this getting too popular, because of fire safety. Fire
safety of a material is about two things: Fire load(kJ) and fire-
resistance(hours). Wood increases fire load, but it has surprisingly good
fire-resistance. Better than steel. The elevated fire load is usually
compensated by sprinklers, and so far wooden skyscrapers have been safer than
concrete ones because of this. Currently fire-resistance is lot more
important, because that pretty much dictates loss of life in regular fire.

But imagine city where you don't have just few wooden skyscrapers, but like
90% of the buildings are wood. Then earthquake hits. Now the sprinklers don't
work anymore, and the fire can spread from building to building. Whole cities
burning was relatively common before 20th century, partially because they
we're mostly built from wood.

>"So wood structures make sense in seismic-heavy regions, especially in the
Pacific Northwest, where a 9.0 magnitude earthquake is expected to hit in the
next 50 years."

>"Ideally there comes a day when people can choose between mass timber, steel
and concrete. We don’t see mass timber replacing those, it just becomes
another option when certain parameters and goals apply to a project."

I hope these cancel each others out. And there will be regular buildings in
between to act as firewall of sort.

~~~
kibwen
An earthquake that shuts off water to a whole city seems just as liable to
render uninhabitable all those concrete buildings (assuming they don't
outright collapse). Wooden structures seem more likely than concrete to
survive the initial quake, even if they're less likely to survive the
resultant fires, so it may be a wash in the end.

~~~
vlehto
Historically the fires have been often even more hazardous than the quakes.

[https://en.wikipedia.org/wiki/1906_San_Francisco_earthquake#...](https://en.wikipedia.org/wiki/1906_San_Francisco_earthquake#Fires)

Something like 30% wood might be the best. But it creates interesting problem,
who gets to live in a wooden building? Who gets to build one?

~~~
kibwen
I trust that the vast majority of the destruction in the aftermath of the
earthquake was caused by fire, but what I'm curious about is the death toll of
the fires themselves, which I don't see in the article. The reason that it
matters is because an earthquake can easily cause structural damage to a
building that leaves it standing but renders it uninhabitable, forcing you to
demolish it anyway. Even structures that are specifically built to withstand
earthquakes aren't necessarily safe to occupy after the quake. From this
(simplistic) perspective, wood is no worse than concrete because either way
you'll be forced to rebuild the vast majority of the city after the big one
hits.

~~~
vlehto
You have good points. My only counter point is that rescuing people from ruble
is easier if there are not much fires around.

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3pt14159
I'm a former structural engineer. I can explain any questions that anyone has.
But in short, wood is one of my favourite building materials. It's repairable,
light, stronger during a fire than steel (although is burns), and it literally
grows in trees!

While it's strength is lower than steel, for buildings less than 10 storeys
tall it's a very good choice, especially if you can do the lower floors and
basements with steel and concrete.

~~~
jseliger
_although is burns_

The article also notes that this kind of wood is "fire resistant." It also
says that, "But the road to approve CLT as a sound building material in the US
has been arduous, with engineers and architects working to prove that it
complies with codes and is resistant to fire and seismic events." Despite
that, though, it still seems like fire is a threat. Is there something I'm
missing? Are the other materials in the buildings sufficiently fire-retardant
to make the issue a small or unimportant one?

~~~
3pt14159
Fire is always a threat. The question is how fast the burning spreads and the
structural capacity during a burn. Fire retardants which are pressured into
the wood, begin to react when the temperature approaches normal wood burning
points (around 275 C) the chemicals convert the wood tars to a carbon char
which provides insulation from direct heat while also allowing the water to
evaporate out of the wood as it more slowly heats. This gives you a _much_
longer horizon to get people out and firetrucks in. You would need a sustained
burn for a couple hours, at which point an exposed steel building would have
fallen anyway.

~~~
fulafel
A typical high rise building will experience some small fires during its
lifetime that aren't structurally threatening. Is the wood building going to
require more repairs or inspections in these cases?

~~~
3pt14159
There would have to be extended contact (more than just a small kitchen fire).
Usually the beam will be repaired or replaced anyway because of aesthetic
reasons, and much of the wood structure will be behind fireproofing where it's
100% safe for at least a couple hours.

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api_or_ipa
Shame they didn't mention the 18 storey wooden residence they're building at
my alma mater, UBC. I wish I knew more about civil engineering and how to
visualize structural loads.

Link: [http://news.ubc.ca/2015/10/01/new-ubc-student-residence-
to-b...](http://news.ubc.ca/2015/10/01/new-ubc-student-residence-to-be-among-
worlds-tallest-wood-buildings/)

------
mmahemoff
The article doesn't really get into the obvious question of fire risks. This
has coverage on that issue: [http://thoughts.arup.com/post/details/302/would-
you-live-in-...](http://thoughts.arup.com/post/details/302/would-you-live-in-
a-wooden-high-rise)

------
douche
Curious what species of timber they use to make this. There's a lot of
structural and and resiliency differences between white pine, Doug fir,
hemlock, and the various hardwoods.

I'm trying to figure out where this product fits into the construction, as
well. I'm reasonably familiar with the general principles of stick-built and
post & beam wooden construction, structural steel construction, traditional
brick and masonry, and poured concrete. Do you just put these panels up as
full walls? Does it still need an internal structure, or do the panels have
sufficient rigidity? What do you do for insulation?

~~~
alricb
It depends on the design, but you can build something using the panels (+
gypsum board) as walls and floors, with almost no other structural members, at
least for residential.

For insulation, the standard approach seems to be using rigid panels on the
outside, either rock wool or foam. This stuff is a good bit more expensive
than stick built construction, so I figure they count the expense of outside-
only insulation (vs. batts or cellulose between the studs) is just a cost that
goes with it. If you're building high-end, you may as well insulate high-end.

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rwmj
How well does this material resist water damage? Recently on British TV there
have been loads of programmes about people building cheap houses (eg [1]).
They tend to be prefabricated off-site from softwood and quickly assembled on
site. I wonder how long such buildings will last if the roof ever leaks.

[1]
[http://www.bbc.co.uk/programmes/b03bjqk4](http://www.bbc.co.uk/programmes/b03bjqk4)

~~~
vlehto
Wooden houses and roofs have been built for long time. I'd be more worried
about leaking plumbing.

If you bring piece of wood indoors and let it dry, it's water content will
drop to about ~17%. If you take it outside and hang it somewhere so that it
catches rain and then dries, it's moisture content will average about ~20% in
most places on earth. Wood has evolved to do capillary action. This means it's
very good at drying, but it's also very good at staying wet if there is
moisture around.

[https://en.wikipedia.org/wiki/Capillary_action](https://en.wikipedia.org/wiki/Capillary_action)

Most wood eating fungi need moisture content of at least 30%. And this has to
be long term, wet week doesn't do anything. But there is fungus called dry
rot, that can cope with 20%. This leaves you practically no buffer, as the
indoors natural is 17%. The catch here is that dry rot needs certain minerals
to ever start growing. Cement and mortar have these minerals. If you build
effective barrier between cement and wood structures and keep the moisture
below 30%, you don't have to worry about rot ever.

Insects are another problem. But it's rare that you get insects if you didn't
get rot first. In those rare occasions, there has been some visible defect in
the surface of the wood. Or alternatively some very infested thing nearby.
Regular paint goes long way.

UK has traditionally had lots of problems in build quality. Mostly because
they didn't take into account dry rot.

Source: Deterioration and preservation of timber in buildings. G. A. Scott
1968. And no, this info has not dated since 60's.

~~~
thrownaway2424
Historically, though, wood structures have been built (intentionally or not)
such that the wood is dried by the heat escaping from within. Modern wood
structures are paradoxically designed for energy efficiency, which is in
conflict with the above. You can't have an efficient building where the
interior heat escapes constantly. Since we're still in the early decades of
this paradox, modern wood buildings tend to be designed to be water-tight, and
when that inevitably fails the structure is destroyed.

~~~
vlehto
Old adage of construction, if you think "but how could this ever get wet?"
you're fucked. Everything will get wet at some point, so everything has to be
self drying.

The plastic film stuff has been tested pretty well for current structures. But
as the insulation thickness increases there might not be big enough pressure
gradient across the structure.

Concrete does not get a pass though. Here in Finland we have had bit thicker
insulation for a while. Even if you don't get wood rotting, you can get mold.
That ruins indoor air quality.

------
karlshea
There's also a big mass-timber office building that just started construction
here in Minneapolis called T3:

[http://www.t3northloop.com/](http://www.t3northloop.com/)

Given the amount I keep hearing about the concept I'm guessing it'll be a lot
more common in just a couple of years.

------
carsongross
I have been a fierce antagonist of modern architecture for many years.

Then I saw some modern architects using natural materials (wood and stone) and
realized that much of my antagnoism was due to the synthetic materials they
were using, and less the style itself.

There is something deeply humanizing about wood and stone.

------
reza_n
Wood framed structures are horrible for dampening the noises from people
walking (or stomping) around. I will never live in a wood structure with
people living above me, its horrible. This is a non issue with steel and
concrete structures.

~~~
gipp
We're not talking about an early-20th-century timber frame. This is a
different material entirely.

A two-second Google search puts actual numbers on this:
[https://fpinnovations.ca/media/factsheets/Documents/cross-
la...](https://fpinnovations.ca/media/factsheets/Documents/cross-laminated-
timber-the-boook.pdf) (page 8). Seems a standard suspended-ceiling type
arrangement provides damping as good as a well-built concrete structure (by
comparison to
[http://www.aia.org/practicing/awards/AIAB025071](http://www.aia.org/practicing/awards/AIAB025071)).

HN comments seem to have a bad tendency to dismiss interesting and potentially
cool ideas out of hand (especially about anything that isn't software) by
citing the first difficulty that comes to mind, without doing even a little
bit of research. As though the many highly qualified engineers putting this
stuff together wouldn't have thought of something as basic as sound
insulation.

~~~
reza_n
The problem isn't really sounds, its the vibration and shock waves which
travel thru the structure. I could never hear my neighbors, but I could hear
and feel every heal strike. Loose metal attached to the structure would
vibrate (air vents, kitchen items). Wasn't trying to tear down this technology
or anything, I guess I just had a really bad experience living in a wood
constructed apartment (constructed in 2013, 5 floors) and I pretty much vowed
to never live in a multi-family wood constructed structure again.

Edit: page 9 in the parent link addresses this. Extremely poor vibration
dampening.

~~~
alricb
Naked CLT sucks at impact damping, but so does naked concrete. You really need
to think things through (methods of attachment for vents and pipes, flanking
problems, etc), and to add some stuff to dampen the impact (on that same page
they suggest adding a suspended ceiling with resilient mounts, giving an IIC
of 62, which is pretty good).

------
MrTonyD
I wouldn't feel comfortable in one of these buildings. I designed and built a
timber frame home, but I look at this "panelized wood" and see a glued product
produced by corporations which are more interested in profit. There has been a
string of failures in similar products as corporations extract their profit
and don't really care how their wood performs twenty-five years down the road.
Glued wood is tricky by nature, and both complex safety and health
implications are introduced by its use.

~~~
beachstartup
_> produced by corporations which are more interested in profit_

how is this different than any other material? or anything manufactured, for
that matter?

fwiw, glu-lam wood has been used in huge structures for decades, and it works
fine.

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jonaf
What about termites?

~~~
thrownaway2424
Termites need somewhere to live. They won't come along to eat a wooden house
in Manhattan, unless there's some habitat for them nearby.

~~~
tro_away_999
Sabotage, buddy. Think about it.

------
hanniabu
Is thermal expansion of the wood not an issue?

~~~
brudgers
Yes. Movement created by volume changes due to changes in moisture contentcan
tend to dwarf it however. In climates with highly variable humidity the
technical challenge can be substantial.

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et2o
This is pretty interesting. What if our housing wasn't built to last
indefinitely, but had a life cycle of maybe 50-100 years? As cities change,
their housing stock could more naturally change with them.

That said, I'm not sure if this style is appropriate for Manhattan today. We
don't need more ten-story buildings in Chelsea for multi-millionaires, we need
more 50-story buildings (still for millionaires, but hey).

~~~
maxerickson
The majority of housing in the US isn't even built to last 100 years (shingle
roofs need replacing after ~25 years and a typical wood building will quickly
deteriorate once the roof fails).

~~~
et2o
Exactly! That's why I suggested wood buildings might be interesting. Lots of
the apartment buildings in Manhattan were solidly built in the late 1800s or
early 1900s and are not going anywhere.

