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
Neither steel nor concrete burn under ordinary circumstances. Wood does. We do not know what exactly happened in New York, and it does not seem relevant here.
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.
Yea, I don't buy those as being sound arguments. I'm sorry I don't just accept everything in a sales pitch. I've seen a log cabin burn, and those were 12" logs, so....
In New Orleans 1972 a concrete and steel building called the Rault Center had it's top two floors gutted by fire, likely arson. The building has been vacant since then, much of it in an almost skeletal state and yet a renovation started last year.
If the Rault Center had sprinklers tragedy could have averted, but I don't believe a wood building could have contained the fire. A wood building certainly couldn't have stood neglected for decades after and still been of any use.
http://www.theadvocate.com/new_orleans/news/article_9ca3a457...
Many contemporary building codes require sprinklers for any building over four stories. To me, the neglect is a sign of economic conditions effecting development more than other factors. For example, if the location was highly desirable and the market for new space strong, redevelopment would make sense.
Highlighting something in an article that shows that a poster clearly hasn't read some or all of the article is "insinuating", and seems to be widely accepted. (And why not - a counter argument based directly on the source material seems perfectly reasonable.)
Maybe the guidelines need to change to say not directly call it out, which is what you seem to be objecting to.
So downvote and say "the article mentions that" with a relevant quote (as per the guidelines). Commenting with "did you read the article?" is just noise.
There's a lifecycle issue which isn't accounted for here. Steel and concrete last almost forever once built - how long do you trust your glue-laminated, termite-sprayed, fire-sprayed timber floor? Especially after a couple of cases of water or impact damage over time...
Reconstructing towers (particularity residential towers) in-use is an incredibly problematic process.
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.
No, they are chemically different cements. However, Roman cements have a tenth the strength of Portland cements, so we can build much bigger structures now even if they won't last as long.
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.
Ordinary buildings are considered to have a lifespan of thirty years. That doesn't mean that they won't be around longer, but that there is often a point of diminishing economic returns in designing for a longer life cycle because maintenance tends to become a primary factor...for example thirty years is a long life for a roof system or the sealant joints upon which modern buildings rely.
I'd like to know that too. Never heard anything shorter than 60 years. But my sources are vague. Stuff heard at civil engineering class and my dad who is construction engineer.
Previous discussion on the same topic (different article but might be based on the same press release, the 3D renders are suspiciously similar):
https://news.ycombinator.com/item?id=12190537
Safety was the first to pop in mind there too -- I guess it won't be easy selling those flats.
It's often surprising how much of building codes are about fire safety. Occasional hazards practically define your day to day environment.
The most fire sensitive part of a high building is the staircase. You want long burn time in fire but also have very little "fire load". (Amount of energy released from material that can burn in typical fire. Typically MJ/sqm.)
Steel staircase gets you 0 fire load but relatively short "burn time". Because steel gets soft at relatively low temperature and more importantly conducts heat very well.
Pure concrete stair case is better, but you get cracking that shortens the burn time.
Wood is surprizingly good for burn time, but you greatly increase the likelihood that the fire will start form the staircase. Which is really big no-no. Sometimes even burning a complete house (starting from somewhere else) is lot better than just burning the emergency exit.
The only really good option is reinforced concrete. The concrete insulates the steel, which provides ductility to the whole structure. With reinforced concrete staircase and stairwell, it's questionable how much you benefit from wooden load bearing structure.
I think it can be done. And it can be done really well too. But you may need to step away from typical architecture and step into something more modular.
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 codes at the time required wide paved streets to act as fire barriers. You get double benefit when you can get your fire engine to the desired location by that new fat street.
And then again reinforced concrete also became available around 1900.
So yes, the code is only small part of all that. But I'd claim it's significant part.
Plus, insurance fraud was at an all time high, detecting accelerants was very difficult, people smoked in bed, people smoked everywhere. As a kid, all I remember is adults lighting cigarettes. My job was stomping out the butts.
Source:watching Goodfellas, and that movie with Bull--forget the name--Backdraft.
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.
I'm not convinced. Only systems that require rigid piping are sewers, air conditioning and sprinklers. (But does air conditioning really require rigid piping?) Sprinkler system is usually quite rigid, but is there any reason why you could not use flexible parts every now and then? Hydraulic machinery routinely has 60MPa in flexible hose.
Laminated wood should have smaller heat expansion coefficient than steel or concrete. Obviously this can turn into problems if you hot air conditioning steel pipe gets longer than the surrounding building.
PVC has significantly higher thermal expansion coefficient than any of these. So the collars have to have some give anyhow.
If you get moisture swelling, you are fucked anyhow. Wooden building has to be designed so that you stay between 17% - 20% moisture content at all times.
Currently wooden small houses have their lateral support done by steel. I'm really skeptical how much this really matters.
Let's say you have 15m long corridor in wooden house and you need sprinkler system along the corridor. If you have temperature increases 30C that may cause your sprinkler system to now be 5mm longer than it was before in relation to the size of the house.
Now we could have suspended the sprinkler pipe to the roof so that every suspension point allows 1mm sliding movement. Or we could have replaces 1 meter section of the pipe with hydraulic hose and leave it slightly bent.
It is 14 floor apartment building and owners had no problems to sell the apartments there. Personally it looks rather ugly especially when looking from near bridge. But then a lot of modern architecture is ugly for my taste...
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.
There's a really interested building material called CLT (cross-laminated timber) that's exceptionally strong and durable, and has good fire resistant properties. In Sweden some have started building houses out of them since their load bearing qualities enables open floor plans. It's like plywood on steroids and you use giant cutters to assemble buildings in a few large pieces
Here's an article, I think there's a few variant of similar materials, not sure which is "best"
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
The one major issue not addressed is: deforestation. Yes, we can make skyscrapers out of wood, but should we? Where do we get the trees from and will they be replaced quickly enough to provide a sustainable future?
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.
If you are reading this thread, you will probably also find the comment thread on the Economist article somewhat informative. (They seem to be moderating it quite well too)
57 comments
[ 3.5 ms ] story [ 126 ms ] thread> 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.
In New Orleans 1972 a concrete and steel building called the Rault Center had it's top two floors gutted by fire, likely arson. The building has been vacant since then, much of it in an almost skeletal state and yet a renovation started last year.
If the Rault Center had sprinklers tragedy could have averted, but I don't believe a wood building could have contained the fire. A wood building certainly couldn't have stood neglected for decades after and still been of any use. http://www.theadvocate.com/new_orleans/news/article_9ca3a457...
> Please don't insinuate that someone hasn't read an article.
Maybe the guidelines need to change to say not directly call it out, which is what you seem to be objecting to.
The guidelines are backwards.
Reconstructing towers (particularity residential towers) in-use is an incredibly problematic process.
Reconstructing towers in use seems like a ridiculous thing to add on to the article.
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
Is that residential, commercial, industrial, all, other?
Safety was the first to pop in mind there too -- I guess it won't be easy selling those flats.
The most fire sensitive part of a high building is the staircase. You want long burn time in fire but also have very little "fire load". (Amount of energy released from material that can burn in typical fire. Typically MJ/sqm.)
Steel staircase gets you 0 fire load but relatively short "burn time". Because steel gets soft at relatively low temperature and more importantly conducts heat very well.
Pure concrete stair case is better, but you get cracking that shortens the burn time.
Wood is surprizingly good for burn time, but you greatly increase the likelihood that the fire will start form the staircase. Which is really big no-no. Sometimes even burning a complete house (starting from somewhere else) is lot better than just burning the emergency exit.
The only really good option is reinforced concrete. The concrete insulates the steel, which provides ductility to the whole structure. With reinforced concrete staircase and stairwell, it's questionable how much you benefit from wooden load bearing structure.
I think it can be done. And it can be done really well too. But you may need to step away from typical architecture and step into something more modular.
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 first Steam-pump fire engines only came into (very limited) use in the 1850s and ICE pumpers in the early 1900s.
And then again reinforced concrete also became available around 1900.
So yes, the code is only small part of all that. But I'd claim it's significant part.
Source:watching Goodfellas, and that movie with Bull--forget the name--Backdraft.
Source: https://www.gov.uk/government/statistical-data-sets/fire-sta...
From following the local fire brigade it seems that the most common source of alarms is people forgetting a frying pan or similar.
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.
Laminated wood should have smaller heat expansion coefficient than steel or concrete. Obviously this can turn into problems if you hot air conditioning steel pipe gets longer than the surrounding building.
PVC has significantly higher thermal expansion coefficient than any of these. So the collars have to have some give anyhow.
If you get moisture swelling, you are fucked anyhow. Wooden building has to be designed so that you stay between 17% - 20% moisture content at all times.
Currently wooden small houses have their lateral support done by steel. I'm really skeptical how much this really matters.
Now we could have suspended the sprinkler pipe to the roof so that every suspension point allows 1mm sliding movement. Or we could have replaces 1 meter section of the pipe with hydraulic hose and leave it slightly bent.
Doesn't sound like an issue really.
It is 14 floor apartment building and owners had no problems to sell the apartments there. 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.
Here's an article, I think there's a few variant of similar materials, not sure which is "best"
http://www.popsci.com/article/technology/world%E2%80%99s-mos...
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.