The Case for Wooden Skyscrapers

There's a reason for that. My father in law was a fireman who retired as chief after 45 years.

Fires are rare today -- but were incredibly common during the 60s and 70s. He was at an average of two a week in those days. It was common enough that insurance companies had "protectives" who were firemen to go in and pull out your furniture.

Fire is rare because of those codes today.

The building codes are about life safety of which fire safety is a component alongside more common hazards such as trip and fall; electrocution; cholera, bubonic plague and influenza; and plain old collapse.

From a practical standpoint, the biggest issue with wood construction is not fire but dimensional change due to moisture [both bulk water and humidity] in addition to dimensional changes due to temperature. The differentials with other materials make systems [such as HVAC, electrical, life safety] more complex mechanically.

In terms of steel, intumescent spray fire protection, masonry, and gypsum board are common alternatives to concrete for fire protection of steel. As a tangent to the issue of differential expansion, the reason reinforced concrete is practical is because steel and concrete have very similar coefficients of expansion as moisture and temperature vary.

There's a building in Portland that's going to be twelve stories tall and built with CLT. My uncle works with one of the companies involved in its construction which is how I heard of it: http://www.structurecraft.com/projects/framework

> Personally it looks rather ugly especially when looking from near bridge. But then a lot of modern architecture is ugly for my taste...

I agree with you 100% there. That is a particularly ugly building.

Presumably, having not read any, this is what building codes cover. So in many structures the effect of impact damage would be the same. With water you have more of a point.

Reconstructing towers in use seems like a ridiculous thing to add on to the article.

Roman concrete lasts forever. Modern concrete reinforced with rebar and exposed to the elements lasts about fifty years.

Reinforced concrete suffers from carbonation. The concrete is base, but slowly get's neutralized by carbon dioxide. Once this has been done, the concrete no longer chemically protects the rebar inside. Then if we take into account that most concrete is porous and has moisture content, that rebar is going to rust relatively quickly. When it rusts, it expands breaking away the covering cement.

Typically reinforced concrete has lifespan ranging from 60 to 150 years. Wood in colder climates often has similar lifespan.

https://en.wikipedia.org/wiki/Concrete_cover

No material is maintenance free...

My timber floor just had its 70th birthday and it's got a lot more in it. That said, it burns well and has borer in it.

Lightning is dealt with by lighting rods. Seismic zones are very non-obvious as factors like eigenfrequency of the building comes into play, not just bare static resistance to stress.

Wood has a particularly good response to bending relative to steel, masonry, and concrete and is likely to perform well relative to other materials during seismic events.

I looked at it the opposite: We can sequester carbon in buildings this way. I haven't done any numbers and presume it's probably small for global warming, but I understand that using concrete put huge amounts of CO2 in the atmosphere, so maybe decreasing that contribution would count for a lot.

You can replace (replant) trees faster than you log them. How are you replacing the steel you're pulling out of the ground? You can recycle steel, but there is a limited supply and extracting it is energy intensive. We can grow an almost unlimited number of trees, and each one is a carbon sink to boot

This is getting dinged, but it's a serious concern.

There are only so many board-feet (or linear meters) of high-quality timber available in a given year, and construction (and reconstruction) of cities was responsible for deforestation across widespread areas -- San Francisco denuded most of the San Francisco Bay Area, for example.

Deforestation in Europe from the 1600s onward had a great deal to do with fuelwood consumption, particularly for glass and iron manufacture. Iron used charcoal, at the rate of about 40-80 kg of source fuelwood per kg of produced iron. Structural wood isn't used at quite the same rate, though it remains a concern, particularly for high-yield-strength. Composite timber (plywood, particle board, and other types) reduces the quality requirements somewhat.

There are no termites in colder climates. The material can be coated to precent any insect from eating it. If you think avout what happened in New York 15 years ago today one might argue steel and concrete burn just as well as wood

You may have missed them but it is worth pointing out these two tiny sections of the article:

> In general, a large mass of wood, such as a CLT floor, is difficult to burn without a sustained heat source—for the same reason that it is hard to light a camp fire when all you have is logs. Once the outside of the timber chars it can prevent the wood inside from igniting. The big urban fires of the past, such as the Great Fire of London, which occurred 350 years ago this month, were mostly fuelled by smaller sections of timber acting as kindling. Prospective tenants would doubtless need lots of reassurance. But with other fire-resistant layers and modern sprinkler systems, tall wooden buildings can exceed existing fire standards

> What about woodworm and rot? “If you don’t look after it, steel and concrete will fail just as quickly as timber,” says Michael Ramage, head of the Centre for Natural Material Innovation at the University of Cambridge in Britain.

You didn't read the article, did you?