According to the linked article[1] there's about 1.1 Tt of concrete on the planet. At a density of 2.4t/m³ that's 458 billion m³ or 458km³. That'd be a cube of with a side length of 7.71km or about the height of Mount Jannu[2] from ocean level.
And with most of it being poured in the last 20 years in Asia.
In China, people don't believe me that Americans live in wooden houses like they see in movies. Some think it's some kind of a set, or super-conspiracy by the party to render America in a bad light.
That's ironic, since wood construction has a much longer history than reinforced concrete, and I'm not by any means convinced that the latter will be as durable.
I think the major advantage wood construction has over concrete is that individual wood elements are replaceable. It would be hard to ship-of-Theseus a reinforced concrete structure.
Plain reinforced concrete is fine to repair and work with. Very basic: Erect temporary supports around the area if its load-bearing, saw-cut/hammer out the working area, splice and retie any reinforcement, prepare the existing concrete surface for a fresh pour, pour and cure.
Certainly more involved and time consuming than, say, replacing some siding or moving a wall inside a stick built house but its all doable.
Most houses last basically forever with "proper care", the question is how difficult/likely is 'proper care'
Regular reminder that stainless steel reinforcement exists, is used bridges and it's use outside is growing, and it will last a thousand years.
Also there is Basalt, carbon fiber and even reinforcement out of used wind turbine blades, which is used in Britain for HS2, and other non-steel reinforcements, which can give you a structure nearly impervious to weathering.
On wood: In Europe we've been using Mass Timber for decides, and it's really good from Carbon perspective and outperforms RCC for small to medium residential and office buildings. Probably not going to replace RCC in infrastructure and industry, but what do I know
Stainless reinforcement is definitely not guaranteed to last 1000 years. Most grades of stainless are susceptible to stress corrosion cracking in any environment containing chlorides (even at relatively low levels), which is pretty much any bridge, industrial, or habitated structure - everything from road salt, to bleach, to chlorinated tap water can be a problem over a long enough period of time.
This has been a big issue with stainless steel climbing anchors and hangars, as it leads to sudden catastrophic failure with little warning, as you don’t get rust like normal steel. Some areas near the ocean have had failures in as little as 5 years - faster than if they’d used normal steel.
Regarding climbing anchors: Anybody expecting to use steel near the ocean and having it last, is in for a really bad time. Ti glue-ins are really the best way to go near water. Plus, I'm sure you're aware of how many variables there are.
Even 316 rusts and corrodes, and that should be fairly obvious to most users if they actually look at the bolts before trusting them.
It's shocking just how much seawater will corrode steel. If you look at pictures of shipwrecks like the Lusitania and Titanic they've degraded a lot since they were first dived to in the '60s and '80s respectively. The former barely even resembles a ship now.
Agreed, what got people for awhile is that while there is sometimes visible rust - sometimes there isn’t - and even then nothing like normal steel or iron. Then it fails. Or doesn’t.
Modern bridges made from concrete are not designed to last more than a century. I believe the expected usefulness of something like a cable stayed bridge is around 100 years. Compare that to a suspension bridge which can be used almost indefinitely.
Some of this is selection bias, but many structures where removed because people desires change over time rather than some issue with the structure it’s self.
Large dry laid stone can easily last thousands of years as long as the foundation is solid. Consider the pyramids both in Egypt and South America plus a host of other very old structures. However, you need to avoid tension, earthquakes, and unstable ground, can’t build very tall etc. High construction costs, slow build times, and serious limitations in what structures are viable shows just why we mostly abandoned the technology.
Mortar is basically indefinitely replaceable with constant maintenance and has lower upfront costs. So it’s generally a much better option.
Reinforced concrete is easier to maintain indefinitely than wood, because it's easier to seal against moisture, especially in harsh environments. Just because there are plenty of poorly built/maintained reinforced concrete structures, doesn't mean that it can't be built for longevity.
Maintenance of steel reinforced concrete is an all-or-nothing affair. You either get it right and seal everything perfectly and monitor everything perfectly and repair tiny cracks before they allow moisture to get in, or you're sunk. If surveillance is lax for a few years you can easily end up with damage that can't be repaired.
Wood construction, on the other hand, is extremely easy to repair. You can cut away sections and replace them piecemeal, essentially forever.
Wood gives you the ability to continuously build a Ship of Theseus, while structurally compromised concrete structures often require you to tear them down and build them again from scratch.
It's relatively straightforward to overengineer concrete to the point where it will take many decades, not just years, of neglect for damage to become unrepairable.
A lot of this discussion is comparing apples to oranges. Reinforced concrete often serves applications that wood is simply unable to perform in (bridges, heavy duty foundations, dams, retaining walls). And yes, poorly maintained, especially prestressed concrete in those applications will deteriorate and fail - but the structure would be impossible with wood in the first place. In more light duty applications wood and concrete can both serve well, but good luck protecting a foundation made of wood from water intrusion. For light duty applications there is no argument that concrete can be overkill and wood can be very appealing.
> A lot of this discussion is comparing apples to oranges.
I agree that wooden houses are not comparable to reinforced concrete bridges. But the part I'm trying to highlight is that being able to easily inspect a structure is a critically important aspect of maintenance, and that most reinforced concrete is inherently difficult or impossible to inspect. The fact that exterior waterproofing is relatively cheap is only incidental.
It's not enough to overengineer a bridge and say it'll last a hundred years if you don't have a reliable way to determine when the bridge is no longer safe beyond year 70. Kicking the can down the road is not a viable long-term strategy. We're about 100 years into widespread use of reinforced concrete and are now starting to see the occasional catastrophic results.
Potting steel in concrete is done because it's cheap and easy, not because it's particularly maintainable. It's inherently difficult to inspect the structure when you build things this way.
> especially prestressed concrete
Agree. Unbonded, post-tensioned concrete (where you can replace individual strands) seems like the only reasonable approach to me, but building this way and doing all of the inspection and maintenance is way more expensive than the "do almost nothing" approach for rebar concrete. But the benefits are only realized after 100 years, so nobody has the incentive to design this way.
> you don't have a reliable way to determine when the bridge is no longer safe
I have a hard time believing this. Despite the ridiculous claims of another poster in this thread (that rebar just spontaneously and completely turns into rust) properly formulated and surfaced concrete and steel don't just rot on the inside with no external signs of decay. If you have repeated water intrusion, you will see seeping and cracks. If you have increasing stress, you'll see spalling. You can core concrete, drill out and patch rebar if you have spot damage.
In general I find the sentiments in this thread bizarre since the vast majority of long-lasting buildings now and in the past century are made of concrete (many of the more modern ones have a concrete foundation and wood or steel superstructure). You don't see many old wood structures because most of them decayed and were torn down - there's a reason why you don't see many wooden bridges standing. Concrete is the closest thing that we have structurally to something that can last forever, and we're learning more about how to make it last longer all the time.
Let me know if you have links that discuss maintainability of concrete in this context. Would be glad to learn more.
I believe there is a very unfortunate example of this in Miami in the recent condominium collapse.
A bridge recently collapsed in Italy.
Etc.
So the problem of failing concrete structures is not 'theoretical' but a very real issue. Even though most concrete construction does seem to last pretty well.
Sure - my main point was that reinforced concrete will fail concretely and not only theoretically unless maintained. I was not suggesting it could be replaces.
Why is reinforced concrete easier to seal? Why couldn't you apply the same sealant to wood? And why wouldn't you have the same issues, such as when you punch a hole in the exterior to mount something, or run wires, etc, you now have to make sure that sealant stays in good shape? Or expansion joints?
I wonder if wood construction is more forgiving than concrete once you get to a point where it was neglected for some time. Wood will rot and need replacing, but if your concrete is ignored and the rebar starts crumbling, you can’t just slap fresh concrete over it and call it a day, right?
Rust isn’t load baring, it’s effectively replacing steel with a powder which is a huge issue if you needed the steel in the first place. Cracks from expansion make both this worse and make it obvious, but even without that it would still be a critical failure.
Not for reinforced concrete, the rusted rebar is still rusted after repointing. Which causes ever increasing internal stress and lower strength over time.
The only way to fix it is to remove existing rebar and replace it which isn’t viable on most structures.
I would imagine that a lot comes down to maintenance, especially roof and siding maintenance.
If you keep the water out, there's no reason why 2x4 and sheetrock shouldn't last a good long time.
I live in New England, and there's plenty of old post-and-beam construction that's held up for a couple of hundred years. Some houses still have their original interior trim and softwood floors, and if that holds up, I can't think of any reason why 2x4s shouldn't.
But old New England construction lasts because it's maintained. New roofs, new clapboards every 50 years, regular painting, interior repairs and renovations. With land costs what they are in many regions, it's cheaper to take care of a good house rather than just letting it fall apart over 50 years.
The timbers in those old post and beam houses is far different than almost any wood you can find commercially today. Old growth wood from 200 years ago grew slowly, and the rings are compressed due to this. Unless you're building a new P&B home from reclaimed timbers, I doubt it will last 200 years.
If concrete is reinforced, even with proper care, physics will get you eventually. It'll happen faster if you're near a coast. It'll take longer if you're inland. But eventually, the inevitable will happen. Our reinforced concrete structures will never last as long as, say, the Pyramids.
Wood will last longer [than reinforced concrete], again, with proper care. But in the end, entropy wins against wood as well. [And again, wood will never outlast the Pyramids].
In civil engineering, there really is no such thing as a free lunch. All materials come with drawbacks.
As iconic as the pyramids are, they're not very useful. A better comparison may be the Pantheon in Rome. Nearly two thousand years old and in continuous use throughout its life. There are a number of other Roman structures that have seen continuous, heavy use for over a thousand years.
There are actually quite a number of ancient temples, churches, bridges, castles, and roads still in use throughout Europe, Asia, and the Middle East. Hōryū-ji [1] in Japan is a 1300-year-old wooden Buddhist temple that's still in use today!
> Our reinforced concrete structures will never last as long as, say, the Pyramids.
> Wood will last longer, again, with proper care.
I'm curious to understand why as this seems completely counter-intuitive to me (someone with no expertise in materials science or building things!). Can you elaborate?
What does the caveat of "with proper care" actually mean? Isolation from all the elements? Does routine maintenance count (replacing deteriorating materials? replacing fasteners? reinforcing?)?
A wood structure properly taken care of does not seem like it would last longer than a pyramid or a reinforced concrete structure, if each of those is taken proper care of. But this is a hunch, not data, and based on nothing remotely scientific. I'm fascinated by this kind of thing; I appreciate any tidbits you can share!
Concrete is strong in compression, but weak in tension or shear forces. To solve that you reinforce it with rebar (basically steel bars). But concrete is porous to water, and steel rusts. When it rusts it expands, which damages the concrete. The only ways to escape that is with coating the rebar (hard to do well) or reinforcing with something else (not many options we know of). You can try to prevent or patch cracks in the concrete to slow down the process, and you can use more rust resistant steel. Both of them prolong the lifetime a lot, but they only delay the inevitable.
Wood is simpler, because it isn't a composite material. You have to prevent it from rotting and from being eaten, but on a timescale of a couple decades we can do that quite well. Also with wood structures it's often easier to replace small parts as soon as damage occurs, which prolongs the overall lifetime (similar to steel structures, but unlike reinforced concrete).
Basically rust is the problem, so if you are scrupulous on upkeep (read, spend money) it will last much longer than if not. How long is also enviroment dependents (temperature swings, salt air, emiisions etc. can make it worse)
What about prefabricated houses in post-communist countries? You definitely can't accuse them of using highest quality materials nor spending loads of money on maintenance, but I haven't heard about major failures and there are probably millions of such blocks of flats out there, built mostly between '60-'80 using a couple of different variations of the technology (some involving pre fabricated pieces of reinforced concrete connected with steel joints). I think they were estimated to last 50 years or so, but there is still large proportion of the population living in such houses in some countries nowadays.
Sorry, I only got curious and started looking into it after the condo collapse in Florida. Every reference I can find on the subject says 100 years is the max life span of reinforced concrete. Not being a structural engineer I took it at face value.
Non-reinforced concrete has to be built bigger, but can last a long time. The coliseum is still up - Hoover Dam will also probably last awhile. And that's without much maintenance.
Smaller non-reinforced structures are harder to build. You have to use the concrete to hold itself up which requires a larger structure.
So you're left with reinforcement. There are options for non-rusting rebar, and non-rusting coatings, but I believe they're expensive. Also, any nick or scratch in a coating ruins it. There's also unique and novel research for non-rebar reinforcement - again expensive.
Here in US most buildings are built to last X years. So long as the rebar lasts longer than X, they'll use rebar. Increase X via regulations, and the quality (and cost) of the buildings in that area increases. Otherwise the bidder with the lowest cost of materials is most competitive. Anyone know what it's like in China?
Small nit not to take away from your larger point - I'm not sure the colosseum is a good example of a concrete structure for comparison to the concrete buildings of current age being discussed. The colosseum did use concrete for the arches, but was primarily built of limestone block secured with metal clamping. Then plenty of brickwork was used. Concrete was integral to the colosseum, but (I believe) a relative minority of the material on the whole.
> There are options for non-rusting rebar, and non-rusting coatings, but I believe they're expensive.
Galvanised rebar is omnipresent around the world. I believe even mandatory in some countries.
> Otherwise the bidder with the lowest cost of materials is most competitive. Anyone know what it's like in China?
Just as you said. Construction companies save on everything. GFRP rebar got adopted in China not so much because of advantages, but because of code allowing for lower concrete cover with it, as I heard.
In Marina Del Rey, the rebar in the concrete sides of the marina are fed a trickle of electricity to prevent corrosion. I'm not sure how common this is though outside of marine environments.
Keeping it dry and sealing large cracks helps, but reinforced concrete breaks down on contact with air so not really. Best option would actually be keeping it in a vacuum, but that’s just not cost effective.
Concrete is very durable. It is reinforcement that rusts and causes thermally induced stress as steel expand and contracts at different rate than concrete.
Reinforced concrete buildings have better thermal and sound isolation. They are obviously more resistant to damage. Proof of this are Khruschev-era Soviet apartment blocks that are standing today.
A condo I lived in had brick walls between neighbors - definitely a huge plus compared to drywall in apartments where the neighbors can hear you turning on the tv at whisper sound levels.
> Reinforced concrete buildings have better thermal and sound isolation.
Thermal conductivity of materials are telling different story [1]. Polystyrene or mineral wool are good for insulation because they have low thermal conductivity 0.032 - 0.038 W/mK (these values are not exact obviously, you can also find mineral wool with values 0.033 not 0.038 but that is just detail). Timber here is 0.14 - 0.17 W/mK. We can find also concrete with 0.16 which is pretty low for concrete but unfortunately that is just aerated concrete which is different from more dense - reinforced one.
So for example in my home country (in central/eastern Europe) where we have Soviet apartment blocks and decide to insulate them we need to cover them with 30cm thick layer of mineral wool or polystyrene foam in order to meet current standards for thermal resistance. Most of them are already insulated at least decade now (unfortunately with just 10-20cm thin layer).
The last building I lived in was reinforced concrete. It was great, I definitely couldn't hear the neighbors, except I could still hear the people upstairs walking around in what sounded like tap shoes at 2am on Saturday nights. Some people just have more fun than me.
Concrete has horrible greenhouse gas emissions issues that wooden construction doesn't.
The chemical reaction for the cement in concrete generates C02 in a 1:1 ratio with the amount of cement produced. Unless you're capturing it you release 1 ton of C02 for your 1 ton of cement. Steel for rebar is even worse, the ratio of C02 generated is greater than 1:1. None of this includes any of the energy you used to heat any of the ingredients either.
Even plastic is better, some of the Carbon & oxygen get sequestered in the plastic.
A process to completely sequester or not generate any C02 in the production of cement & concrete that was cheap & easy would be a Nobel prize winning innovation. If the whole world switched to that it would be more significant than switching all vehicles in the world to electric.
Is there any comparison available? I've seen concrete and masonry houses built, and while the concrete has a greater carbon footprint, there's little waste compared to wood houses with drywall: wood treatments and coatings, insulating foam, materials wrapped in disposable plastic sheets, etc. Modern wood houses are far from just wood.
I would rather live in a cheaply made wooden house than a cheaply made concrete one. The simple common way to build a wooden house is massively redundant. Concrete houses use post and slab, even in poor countries. So in Nairobi, they were having six building collapses per month.
Your source seems to contradict 'six buliding collapses per month':
"A six-story building collapsed Friday night in Nairobi, killing at least a dozen people. Several buildings in Kenya have collapsed in the past year. Why?"
Easy to work with is the main one. I can do almost everything myself with less time, less equipment, and less chance of injury.
Cheaper (where I am). Let’s WiFi signals through easier, so I need fewer access points.
I’ve worked with both, and the main advantage of concrete would be the sound insulation. But I feel like a quality wood + drywall + insulation installation can come close enough for residential purposes.
Wood is cheaper up to certain scale, less environmental impactful, and flexible in the face of dynamic load changes and construction.
For larger construction, pumped concrete is cheaper to build. It’s generally (but not always) more fireproof without special measures being taken.
You think that concrete is stronger because it looks solid and heavy. In many cases, concrete or other masonry buildings are actually clad buildings with wood or other framing. Also, generally speaking a small scale, poorly built concrete structure will be more solid than a poorly built wooden structure.
I live in an urban house in upstate NY, it’s a wood frame house built in 1925. It’s not a luxury or high-end construction, but there’s no structural reason that it won’t be standing in 2125. Keep a roof on it and control storm water and you’re good to go.
Well, some American states are extremely hot and dry by UK standards - meaning issues like rot and rust are less of a problem.
And Americans build a lot of detached single-storey houses [1], which mitigates some of the disadvantage of wood: Noisy neighbours? You've got a six-foot-plus air gap between your houses. Fire risk? Escape is trivial when every room has a ground floor window. Rain getting onto the wooden walls? Much reduced by a porch stretching around the entire building. Needs regular repainting? Easy when it's a single-storey building.
Wood is also substantially cheaper in the US than in the UK - so while it might not look like a cheap material from the prices at British wood stockists, Americans who call it a cheap way of building aren't paying those prices!
6 foot between detached single family homes only in the densest old city neighborhoods. The legal minimum in most places is now 10. These would be properties that many Americans describe as “right up my neighbors ass”. Your average home in the burbs is going to have 30+ feet between them, especially in the hot dry (read: developed post AC) areas of the US you’re talking about.
> Rain getting onto the wooden walls? Needs regular repainting?
Most “wooden” US homes do not have wood siding. Vinyl is extremely common, and most homes that predate vinyl have had vinyl installed because it eliminates the maintenance associated with painted wood. Mine is decorative masonry. (And I wish I had vinyl)
> Most “wooden” US homes do not have wood siding. Vinyl is extremely common, and most homes that predate vinyl have had vinyl installed because it eliminates the maintenance associated with painted wood. Mine is decorative masonry. (And I wish I had vinyl)
I thought all new homes in the past decade or so came with cement fiber siding like Hardibacker, Durock, or Wonderboard. I have not seen new construction with vinyl siding in a long time (west of Rockies).
Where do you live that vinyl is that common? Where I live almost every house has hardiplank or cedar siding.
Personally I don’t like vinyl siding because it looks cheap and it melts (this seriously happened to a friend of mine - the sun reflected off the windows of his neighbors house and melted his siding.)
This is an interesting post. You wrote: <<Wood is also substantially cheaper in the US than in the UK>>. This is surprising, as it should be easy to import wood from the Nordics or Russia. Maybe the transport costs are to blame?
The UK has wattle and daub wood frame houses that are 500 years old, too. The hatred for wood frame houses in the UK and Ireland is a strange thing, especially considering the pyrite scandal a few years back, the mica one now, and the hideous carbon footprint of concrete.
There are a few people fighting this, https://gracedesign.ie/ makes stunning beautiful house frames, and I'm having my own house built in wood right now. By coincidence, so are the people in the field next to me. But there's decades of prejudice to overcome.
Door and window frames are the only wooden element in most houses. You can instantly see if they have never been replaced, and after 70 - 80 years they look quite old. Now imagine the whole house looking like that.
I live in a 100 year old wooden house. Its got some character due to modifications and its era (1920's). But its been well maintained and there is no apparent reason it wouldn't survive another 100 years.
My last house was built in 1964 and the wood would be considered extravagant by today's standards. It was no fancy house, either, just a garden variety ranch. But it had decent (as I said, not fancy) oak hardwood throughout. Actual 2x4s that weigh 2x as much as fir studs today. Old-growth cedar siding. It was built in an era where it was no big deal to use good wood for everything.
The codes are moving back to 2x4 walls. Since the 1970s 2x6 started becoming common, but that reversed when someone realized you can put 2 inches of foam outside the 2x4, have the same wall thickness (meaning common doors/windows fit), and there is no break in the wall insulation. The wood itself in a board is not great insulation, so the foam around the whole house even while it seems to offer the same r value offers more. (you can also get foam with r values much better than wood, I'm not aware of code requiring that, but some builders offer it as an upgrade).
Note that this foam is foil faced meaning it insulates against radiation energy as well as conduction or convection.
That must be regional. I live in the PNW, and it's pretty temperate here (the last few days notwithstanding...). House construction is still 100% 2x6 for exterior (and interior load-supporting) walls. Most houses are not being built with foam on the outside. I've heard of that happening where it's legitimately cold, though.
I'm sure it is regional. Close climates need more insulation than warmer ones. I've seen variations of this in El Paso (only 1 in foam) for high end housing where the cooling advantages can be sold.
I doubt interior load supporting walls are 2x6. Often there are internal 2x6 walls, but that is to allow extra space for plumbing - 2x4 is plenty strong enough for load bearing in most houses, but toilet drains/vents don't really fit.
This works for bigger studs too! The options presented for the house I'm building now are 70x200mm (about a 3"x8") stud with 200mm interior insulation and 100mm exterior. That's for a very well insulated wall, though.
It doesn't, the 2x6 "fad" went on long enough that you can buy doors and windows sized to that standard. You can use any thickness of wall you want, but if it isn't same thickness as a 2x4 or 2x6 you will have to put forth extra effort to make your doors and windows fit. Use a standard dimension wall and you can buy those to fit.
Not a big deal for a qualified carpenter, but enough extra labor that you will pay extra for it in addition to materials.
This is clearly regional. I'm in the US where we don't measure in MM. Different parts of the world will have different standard sizes. you might be able to import a US standard door if you wanted to use 88.9mm widths for some reason (there is more than enough tolerance to round that to 90mm), but it would be extra effort on your part. The hard part about importing it often codes are designed to limit this, so even if the US door is better it might not meet some standard that shouldn't even required. (this goes both ways, US standards often require things just to limit imports as well)
My current home is a dirt cheap one built during the explosion in housing post world war II. It's wood on top of poured concrete slabs for a foundation (yes, ok, some concrete - maybe something else could have been used? brick?). It has no structural issues. (it has issues due to stupid design decisions from stamping out homes at that time, but none related to the wood).
It is now 60 years old. I imagine it will be standing for a long time to come.
My mom lives in a 110 year old house in one of the wettest regions of the United States. The walls are a bit thin by current standards, just 2x4 even though it's two stories with a basement, but it's holding up fine. Rot has never been a problem. She just keeps up on the routine maintenance -- painting about every 10 years, roof shingles every 25 years. It would still be fine 100 years from now, I expect, though I'm certain that when she passes someone will buy the house, gut it, modernize the wiring, plumbing, and insulation, and then rebuild the interior to look as original as possible. Very popular around this area.
Old houses are amazing if you need to live in them without modern heating and cooling. They're built to work about as well as possible, under those circumstances.
They suck if you want to retrofit them to have modern heating and cooling. The high ceilings, giant windows on all sides, large open attics (vital for temp control without AC!), and generally poor sealing (=great if you need them to survive temp and humidity changes throughout the year, and not turn into a giant mold farm like a modern house would) all work against you.
I looked at a house in Boston that was built in the 1700s, and it had the opposite problem. Ceilings were like 6.5 feet, felt claustrophobic.
Where I live now, ceiling heights are going back up. 10 years ago it was common to have 9 foot ceilings on the first floor, 8 foot on the second. Now it's common to have 9 foot on the second floor as well. And there are a not-insignificant number of houses being built with 10 foot ceilings.
In an air conditioned house, I do not see the purpose of 9ft and 10ft ceilings other than vanity. It just results in more cost to condition air that is above your head.
I would rather spend less on my utility bills, and conserve the energy.
I don't feel too strongly about it, though on balance I like the open feel to 9 foot ceilings. It seems to be standardized on most new houses these days, so unless I have another house built I don't expect to be able to make a choice.
I live near one of a state's first cities in the Midwest. Many of the original buildings, brick and wood alike, are still standing. Those are between 140 and 180 years old.
Many (brick and wood alike) were destroyed by fires and floods.
All in all, the lifespan of wooden structures is more than adequate, and significantly cheaper.
There are whole neighborhoods of 120+ year old wooden houses in the US. If they're cared for they look great. If they're not, they look like shit but are still standing and basically fine as long as water's been kept out (no long-term roof leaks). They're largely made of WTF-good timber by modern standards, but worse construction in other ways (balloon framing is common, for instance, and fire protection is otherwise poor as well).
Further, they're designed to exist without modern heating and cooling, and many still don't have those (or they don't work very well). Yet they stand, and often still have perfectly-aligned original wooden trim work, despite being subject to swings in internal temperature and humidity that'd ruin a modern house in a hurry (modern ones are too air-tight to survive that, aren't built with any care to wood grain direction, and use much lower-quality timber throughout, including for trim, though they may benefit from extensive use of dimensionally-stable plywood).
I live in one of those neighborhoods and the thing that kills our houses (aside from leaking roofs) is poor foundations. I've literally never heard of one of these houses falling over because of a structural issue with the actual timber it's built from. It's either that the wood has rotten because of roofing issues or (more likely) the rubble stone foundations fell apart
edit: and even if some of the wood has rotten you can almost always just replace or sister up that piece and be absolutely fine.
What's interesting to me is you have Europeans marveling at houses built of flimsy wood instead of strong brick and concrete. Yet except for occasional water and termite damage what's failing in these houses is the concrete and brick foundations. Not the wood framing.
Hell, concrete foundations fail badly enough to need repairs pretty commonly within the first few years on new houses, and I don't just mean normal settling. Doing concrete right takes a lot of waiting and is highly dependent on the weather, which usually means even more waiting (for enough days in a row of the right weather). Builders (understandably) hate anything with that kind of potential to throw off a schedule—unpredictability can increase the total time construction takes by much, much longer than the individual delays themselves—so some of them cut corners. They also don't like to let the ground sit as long between excavation and pouring as they should, because time is money.
I wouldn't want a concrete house in the US without inspections so strict that the inspectors basically dictate when & how concrete may be poured, and/or laws explicitly breaking corporate liability protections for failure of concrete within some long time span, or otherwise ensuring that builders care very much that their structures last several decades without needing repair. I suspect they'd be crazy-expensive as a result.
Some people like the old style of architecture, which is possible but very expensive to reproduce with modern techniques (custom masonry, built in carpentry, that kind of thing)
my house is well over a hundred years old and was built out of wood, it's been well taken care of (still has the original roof, even!), why exactly would I want to rebuild a perfectly good building? These buildings have been standing a long time, they aren't exactly going anywhere
My home is 100 years old and probably one of the younger houses in the area. Many homes have been renovated in part of over time. Things like adding electricity, changing the electrical to be modern, adding additions, converting rooms and adding modern plumbing, changing siding and roofing, HVAC installed, etc. So over time, the home is modernized but the original frame (the "good bones") are still there.
And let me tell you, those old frames are unbelievable if they've been taken care of. If you do a renovation and open it up the wood is thick with tight, straight grain. A lot of these homes were built with old growth timber that was abundant at that time and unavailable today. The natural aging of the wood has dried out moisture and resins and makes for stronger lumber, albeit lumber that is more brittle which isn't a concern for how it is being used.
There's a good chance the wood was quarter sawn as well and if you have the original floorboards there's a good chance they were quarter sawn back then too. This, again, makes for better construction as the wood won't warp as much.
That's an over-generalization which is very often wrong. Massive timber (including things like CLT or Brettstapel) are very fire resistant and very safe in a fire. The outer layers tend to char while the rest of the structure is preserved.
To say more: if a large timber beam is exposed to fire and comes out charred, you can often just scrape off the charred part, but for a steel or concrete beam the damage may be fundamental (introducing cracks or permanently changing the size or material properties) requiring the part to be replaced.
You don't want to live in a multi-family wooden house - the noise from above you will drive you wild. With a concrete house you don't hear your neighbors.
I’ve lived in multi family wood homes in the US without issue. It can be an issue with the cheapest construction, but sound insulation can mitigate or solve those problems.
Since moving to Boston I have only lived in multi-family wooden houses, and this just isn't true, at least with modern-ish insulation. I can occasionally hear my upstairs neighbor's dog when she gets excited, and precisely nothing else.
Hm. The only multi-family building I've ever lived in was an apartment complex and it was steel and concrete. I don't think they are typically built out of wood even here, although I've read about some experiments with wooden office buildings as more environmentally friendly. I guess if I was really curious I could look and see if they'd added extra sound damping to deal with that.
In any case, the typical American wooden home is not going to have a family above you. :)
That specific type of construction started in 2009 after the building code was changed to allow it. They are known as a “1+4” or “1+5”, with the first floor being concrete and then 4 or 5 wood floors above. Very economical, and hence why almost all new multi unit construction has been that style for the past decade.
Wood homes is quite an American thing. In many parts of Europe for example, many people live in brick or stone or blockwork or indeed concrete buildings (though raw concrete is mostly unfashionable.)
In New Zealand we have construction not dissimilar to the USA, from how Americans in HN describe house construction. 100+ year old wooden houses are common here.
Construction evolves due to avaliable resources and local conditions. Transplanting a technique from one country to on other won't necessarily work.
If you have earthquakes such as in NZ, USA or Japan building concrete houses does not make a lot of sense.
This statement seems wrong to me. According to [1], 43% or residents in rented accommodation live in single family homes. [2] claims that about 80% of owner-occupied dwellings are single-family homes (but the source seems funky: surely there are more than 80k owner-occupied dwellings in the US.)
A cube with 7.71km side length is so totally foreign to us it is unimaginable. Mt Everest by volume is 59.5 km^3, or about 13% of the volume you've quoted. We are probably more accustomed to think about sizes of conical structures, again due to mountains being the only thing we have for scale. It would be interesting to think how much we'd have to scale up Mt Everest in order to get to a volume of 458 km^3.
I've done a similar mental experiment with oil. The US consumes about 20 million barrels of oil per day. Here is a useful visualization: imagine a (US) football stadium from the air with a huge black cube floating above like something from a sci-fi movie. The cube is about 50% larger on a side than the distance between goal lines. That cube of oil is about how much the US burns in a day.
A lot of the problems with concrete are actually problems with steel reinforcement. Concrete alone is incredibly long-lived and durable, see the Pantheon in Rome. However steel rusts, expands and weakens within decades, even when you do everything right.
Part of that is because they have to other wise the building would collapse on its own.
A big issue people don't talk about is that a lot of the concrete China makes is subpar and not up to spec by US or EU standards - they don't use the right (aka more expensive) grade of sand, so the concrete doesn't bind as strongly as it should. The sand used to make concrete has to have rough edges, something about the surface area, which ironically means that desert sands aren't very useful - they've been rounded by wind erosion and rubbing against other sand grains.
There's a kind of twisted logic to it. If your construction techniques are constantly improving and the high volume of construction incentivizes you to develop more cost efficient construction technologies, then planned obsolescence of buildings is like planned obsolescence of phones. Build soviet block apartments, knock down in 20 years, replace with prefab building compartments with wiring and plumbing built in at the factory. Then export the prefab technology worldwide to take advantage of the infrastructure boom in other developing countries. Isn't build fast, break fast, and learn fast the whole silicon valley ethos?
> In China, 20 year old, if not 10 year old highrises are knocked down.
Isn’t it part of their 12% year on year growth strategy? Whatever it takes to make these numbers happen? Which is also why China builds cities designed for millions of people that remain ghost towns once they’re done: they’re not really built to be lived in but to boost the economy activity via construction costs.
Basalt is a pretty amazing material. This is just one use. Basalt is also used to make insulation, low skid tiles, and corrosion resistant pipe liners.
It's what it sounds like: rebar made from basalt (basalt fibers specifically): melt the basalt, extrude it, mix it with polymers, shape into a REinforcing Bar.
Problem's it's way more expensive than steel. It's also a pretty young material so I don't know how much safety and longevity information we have. Steel's well understood.
The expense is an upfront cost. Using basalt rebar we could be building 100 or 150 year bridges instead of 50 year bridges. We know basalt concrete structures wont fail from the reinforcement rusting away. We just haven't been using basalt rebar long enough to know the long term failure modes.
Basalt rebar does not have the tensile strength of steel rebar. During extreme stress, steel rebar allots time for escape, increasing the survivability of an event. The behavior of basalt is significantly different.
Just different materials, with different performance profiles, that you can use to beneficial effect in different environments. But you have to know and understand the implications of the different performance profiles.
I'm not going to do a whole engineering lecture here, but there is a really good concrete nerd who can outline this, and so much more, for you on his youtube channel if you're interested. He's a good engineer and I've been impressed with the accuracy of the material he presents as well as the accessibility with which it is presented.
For the way we use it, yes. Concrete works well in compression but is horribly weak in tension; a supervisor of mine compared it unfavourably to a ginger nut biscuit. Probably hyperbolic but you get the idea.
Big, arch-y structures like the Roman pantheon work, because everything is in compression. But that's a lot of not-economically-useful space.
In order to use concrete by itself, you have to limit yourself to specific architectural structures which are very much unlike modern buildings - essentially, you can build quite high ancient-looking structures with everything held up on arches (which take up space and material), but you can't build a simple box-shaped building from concrete without steel rebar.
One of the big reasons is ductility. We want structures to show signs of distress before failing catastrophically. With ductile reinforcing (steel), the deformation at which failure occurs is easily 5 times larger than the deformation where yielding occurs. Large cracks will open up, it hopefully gets noticed, and there is a chance to intervene.
With GF or CF reinforcing, failure is sudden and catastrophic.
> Why can’t we use carbon fiber or aluminum or anything that won’t rust?
We can, we do, just steel is super duper cheap, and workable.
Ironically, it's China now who leads the world in GFRC (glass fibre reinforced concrete) construction to get those miniscule cost savings on steel (despite it being world's biggest steel producer.)
There is also basalt fibre reinforced concrete that is supposed to be superior to glass fibre, and can come in workable varieties (heat it up with a torch, and bend.)
To avoid the problems of rust, epoxy coated steel is often used. It costs more, so in situations where the contract is won by the lowest bidder (unless it is expressly required), you don't get it.
So as a result, buildings that could last 200 years start to crumble after 50.
Epoxy coated rebar was a trap, and is now being banned around the world. Paradoxically, the epoxy coat can make corrosion worse than the bare steel, let alone galvanised.
Not sure why you're being downvoted, because you're right, atleast on the west coast of north america. My firm hasn't use epoxied rebar since like 1990, and we removed all references to it on our drawings long ago.
The coatings were super fragile, and often damaged while being placed in the field. Then someone had to come along with magic paint and touch up all the cracks. But of coarse they would never find 100% of them...
He's getting downvoted because more modern versions of epoxy coated rebar are still widely used in new construction. It wasn't the silver bullet for salted roadways it was sold as but it has its place.
We actually can - fiberglass rebar has many advantages over steel, among the first being that it does not corrode and expand. It's also much lighter and easier to transport to and on the worksite.
It is starting to see widespread use in the construction industry, but far too slowly. A quick search on "fiberglass rebar" will return many manufacturers and articles.
I’ve found when you use the proper pronoun — ‘they’ in this case, unless you make concrete — it focuses your thinking.
That is, if you want to know why ‘they’ do something, you’ll naturally ask ‘them’.
But, when you use ‘we’, you’re more likely to just imagine your own solution.
Nothing personal.
‘We’ is the bane of my existence...
In order for this post to be somewhat relevant, I’ll add this... I see corroding rebar as a feature and not a bug; it assists in the natural degradation of concrete and it gives me some comfort to know that the distant future will have no signs of the concrete monstrosities that litter out landscape. Thanks, rebar.
> Concrete alone is incredibly long-lived and durable, see the Pantheon in Rome.
That requires massively overbuilding the concrete structure, and many of the things we mold concrete into simply would not be feasible in unreinforced concrete, it's only strong in compression.
Plus the Pantheon and friends are good examples of survivor bias, for the on Pantheon there are hundreds of insulae which didn't survive.
This is a total misunderstanding of survivorship bias. It would be like encountering a 1,000 year old man and attributing his age to merely survivor bias rather than investigating whether it has something to do with the magical beans he ate.
Concrete is one of the biggest sources of emissions in the world and it feels like a blind spot in our push for greener solutions.
Is there any research being done into alternatives that will scale to what we use concrete for? I've seen alternative home building methods, and different urban planning can reduce the need for large buildings that need it, but I haven't seen good alternatives for roads, tunnels, bridges, etc. Steel sometimes works but has its own problems and is more expensive.
It's funny you should say this - I just recently was on an airplane with a bunch of folks returning from a big Vegas concrete convention. Eavesdropping a bit here and there, it seemed the topic of "greener" concrete was big. The person in the seat next to me was describing how they recently started using a concrete and steel fiber mix so they could pour less and achieve the same strength and durability - the main "customer pitch" she told me was that it would was a lot greener. No idea if any of that is true, but it was interesting to see how focused on it they all were.
Not necessarily. At times, a tiny band-aid on things can be counterproductive. See replacing plastic straws with paper/reusable ones; it's a drop in the bucket, and it's used in part to distract from the much larger overall issue of single-use plastics.
I don't see any evidence that the push against plastic straws is used to distract from other single use plastics.
Indeed, I see the opposite. I see advocacy groups that are fighting against single use plastics using anti plastic straws campaigns as a way to spark conversations about other kinds of single use plastics.
I don't see how paper straws distract from anything. Every time I see a paper straw my immediate thoughts are about how it's not plastic that'll be getting thrown out.
> At face value, these efforts seem benevolent, but they obscure the real problem, which is the role that corporate polluters play in the plastic problem. This clever misdirection has led journalist and author Heather Rogers to describe Keep America Beautiful as the first corporate greenwashing front, as it has helped shift the public focus to consumer recycling behavior and actively thwarted legislation that would increase extended producer responsibility for waste management.
> For example, back in 1953, Vermont passed a piece of legislation called the Beverage Container Law, which outlawed the sale of beverages in non-refillable containers. Single-use packaging was just being developed, and manufacturers were excited about the much higher profit margins associated with selling containers along with their products, rather than having to be in charge of recycling or cleaning and reusing them. Keep America Beautiful was founded that year and began working to thwart such legislation. Vermont lawmakers allowed the measure to lapse after four years, and the single-use container industry expanded, unfettered, for almost 20 years.
No, there are some companies actually trying to create "greener" cements and concrete formulations. We can absolutely split hairs about it, but some are significantly better than conventional and are in the pipeline for use. However, still years away due to regulation testing and standards adoption.
One material that should be used much more in building but isn't: straw!
It's become a recent obsession of mine.
* has a long history of use (no research needed)
* is eco friendly (in fact sequesters carbon)
* cheap
* readily available
* pliable material that is forgiving to build with, even for novices
* quick to erect walls
* is a waste material - usually ploughed back into fields or burned
* has very impressive thermal and sound insulation, so no additional insulation is needed, unlike a concrete walled home or building
I could go on....
Of course not every building or structure can be made from straw bales, but many houses, warehouses or smaller commercial buildings could be. It's a very low hanging fruit in the battle against climate change.
I read that straw is basically outlawed bec it’s hard to make a house with it and still be on the right side of fire safety codes. Especially if you’re using it as part of your insulation strategy.
Yes there is. Geopolymer cement provides an 80% reduction in co2 emissions vs traditional cement. CarbonCure has developed a version of concrete that absorbs co2 during its production, though it cannot be poured and can only be used to make prefab shapes [1].
An issue with these new cements is that there is no economic incentive for companies to change production processes and switch.
It isnt just cost that prevents a switch. Some building codes explicitly state Portland cement as the allowed material. Geopolymer proponents have been working to change building code to stating required material properties instead. Unsurprisingly, geopolymers have taken off in countries with less regulation.
Concrete production represents 4-8% of all worldwide CO2 production. It's a significant percentage. There's talk on sequestering CO2 in concrete itself but I'm not sure how far it has gotten. I do remember some plants in France or Germany having facilities to process clinker byproducts. I wonder how more efficient is that.
Why don’t we focus on the problems we can solve today? Cars, power generation, and improve industrial process that emit green house gasses.
We could solve these issues “today” in a sense. Creating new carbon neutral building materials that last as long as current stuff seems like a huge risk.
That is until the well-connected lobby carbon tax loopholes into the implementation and use the carbon tax yet another tool for regulatory capture to stomp out competition. Or, companies simply shift more production to developing countries to skirt taxes. We can create ecological disasters over there instead...
While I like the idea of attaching monetary costs to otherwise ignored externalities, I don't see the carbon tax having any chance of being fairly and effectively implemented.
Honestly, I think we actually want a high-carbon cement: One full of graphene or other carbon compounds, pulled from the atmosphere. Per the article yesterday [1] we need to remove 2 teratonnes of CO2 from the atmosphere to meet IPCC targets. Maybe some of that will be done by taxpayer-funded carbon sequestration operations that exist only to pump the carbon 'away' in underground reserviors. But I think that if we've laid down 1 Tt of concrete, and could develop something better than that which is carbon-negative, people would be more than happy to pay for that CO2 sequestration, and that progress might actually survive an election cycle.
> Is there any research being done into alternatives that will scale to what we use concrete for?
Flyash, and other pozzolanic industrial wastes. There are literally mountains of it.
Problem? There is no "standard flyash," every power station uses a bit different fuel. Same for industrial wastes.
Second option are natural geopolymers, but they are not that common, and coincidentally, most of countries with a lot of geopolymer deposits are rather rich, and that undercuts economic incentives.
Been looking into graphene and it can reduce the amount of concrete and increase the strength. Of course, can graphene be made at a commercial level and out of the lab
> If future archaeologists do the same for us, what material might they choose to define the 21st Century? Silicon? Plastic? Both are candidates, shaping the world for better and for worse. But if the decision were based on scale alone, then there can be only one answer: we are living in the age of concrete.
"And if its rate of growth continues, it will overtake the total weight of Earth's biomass sometime around 2040."
Rather than impress me with the amount of concrete, this actually impresses me with just how incredibly huge the biosphere is! That's an enormous amount of life.
Concrete is a mixture of different sizes of a strong stone, like granite or silicate in a carefully graded mix of sizes from sand sizes upwards. The idea is to get the final block to be 100% stone(impossible) or as close as practical. You then cement this all together (mixing all the while) with powdered cement. Cement is a mixture of
C3S: Alite (3CaO·SiO2);
C2S: Belite (2CaO·SiO2);
C3A: Tricalcium aluminate (3CaO·Al2O3) (historically, and still occasionally, called celite);
C4AF: Brownmillerite (4CaO·Al2O3·Fe2O3).
This is melted at high temperatures into 'clinker' (when melted it resembles lava from which classic roman cement was made as it collected as a fine volcanic ash).
Rock has water of hydration strongly bound into, when melted into clinker the water evaporates = clinker.
The clinker is ground to a powder and added to the graded mixture of sand and small rocks and water is added - it is then mixed very throughly and the final water ratio is established. It is then poured into the moulds that hold the cement in the final shape you want when it sets. You vibrate and shake well to get the air bubbles out and then you want for it to cure. As it cures the powdered clinker absorbs water and turns into the fully hydrated final (set) form. It can take months to fully set, but usually after a day it is into the 60-75% area of final strength. This makes heat = big things need active cooling, small stuff not so much.
As it cures and very strong matrix of hydrated crystals fills all the space = set or cured concrete.
Reinforcing can be any strong material that is not brittle. Usually steel rebar is OK for a dry life structure. For damper areas you can use epoxy coated rebar, then galvanized rebar, then epoxy coated and galvanized rebar. For the next stage stainless steel rebar is the high cost option. Nuclear power stations use SS rebar in some cases.
Corrosion. Steel corrodes. Steel = FE,(1 atom) corroded steel = FeO (2 atoms = bigger) if oxygen reaches the steel it will make FeO - these 2 atoms are bigger than the one atom of Fe.
This means the FeO will expand with an irrestible force (200 times as strong as concrete). It is this rebar expansion that makes huge cracks = more water in, = bigger cracks etc.
FeO is as weak as kleenex as a support member. so as the concret and rebar turn into powder the strngth of the structure vanishes. At some point you get this sort of collapse - all of which was preventable by proper design and maintenance.
Punishment? imprison them in the basement of one of their badly made buildings and let them spend their life waiting for the inevitable collapse.
Concrete Wiki https://en.wikipedia.org/wiki/Cement
Needs to be the right kind of sand. When your kids are playing at the beach you don't really notice that some sands are better for sand castles than others - and few could care if it was pointed out to them. When you want to make a building last though the properties of the sand matter.
Concrete is good at compression, steel good at tension and reinforced concrete at both. A space elevator needs tension, a lot more than steel can withstand.
You seem to have forgotten than you used to eat rocks just like every other baby. Some of those babies are eating concrete rocks. So some people have > 0% concrete in their body.
According to the linked article[1] there's about 1.1 Tt of concrete on the planet. At a density of 2.4t/m³ that's 458 billion m³ or 458km³. That'd be a cube of with a side length of 7.71km or about the height of Mount Jannu[2] from ocean level.
[1] https://www.nature.com/articles/s41586-020-3010-5 [2] https://en.wikipedia.org/wiki/Kumbhakarna_Mountain