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Comment by Cupertino95014 | Hacker News Reader

Major FLW groupie here. I've been to the Wisconsin Taliesyn, Fallingwater, the Johnson Wax building in Racine, his own home in Oak Park and many of the other homes there he built. I love it.

That said: my brother went with me to Taliesyn. The main thing he noticed was the shoddiness of the workmanship, e.g. glass corners that didn't meet squarely. Still, it's inspiring.

During the Depression, all you needed to move to Taliesyn and study with the master was $500. No skill requirement. Johnson Wax had years and years of water leaking in from the roof, although they finally fixed it and they work in it still.

Steel-reinforced concrete is a time-limited construction technique. Water eventually gets in and rusts the steel.

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Stainless steel rebar is the way to go. It's more expensive, but is becoming popular for bridges, especially ones over salt water. 100+ year lifespan. The price differential is coming down as the demand increases.

Plastic-encapsulated rebar was popular for a while, but turned out to be a dead end. A nick in the plastic and water gets in.

I'm not a civil engineer or even close, but I did note that some Roman concrete structures have lasted 2000 years, and nothing we're building now has any chance of lasting that long. 100 years is not much, considering what infrastructure in developed countries costs nowadays.

it's easy to forget that modern buildings have much more complex loads, higher stress weights, and the added benefit of us being able to calculate strength.

it's kind of similar to the idea a 'craftsman' house used to cost the equivalent of 50k, and now a house is 500k. That's down to electrical service, having gas, appliances, modern codes, and more. shit, it's been so effective at reducing random fires that fire houses now have to include EMS for a reason to exist.

it's cool as shit that a bridge over an ocean can last 100 years, do you have any classic examples of bridges or buildings in continuous use for thousands of years? of course not, it would wear out. the buildings that last are directly proportional to how used they are, unless maintained like a religious building.

Friendly inflation reminder: 50k in, say, 1950 dollars is roughly equivalent to 500k today. But of course one can argue that QoL improvements like you mention are exactly what makes up (some part of) inflation.

> do you have any classic examples of bridges or buildings in continuous use for thousands of years? of course not, it would wear out.

The Pantheon in Rome is famous for having the world's largest unreinforced concrete dome: https://en.wikipedia.org/wiki/Pantheon,_Rome

Various Roman bridges are still in use: https://en.wikipedia.org/wiki/Ponte_di_Tiberio_(Rimini)

Being in continuous use makes it more likely that a building will last long, since otherwise people might tear it down to use the stones elsewhere. (E.g. what happened to the Colosseum.)

If you read up on "Roman concrete" you find out that it used a volcanic sand "pozzolana" [1] which is difficult to find in some parts of the world. There was, supposedly, some American professor trying to find a recipe for concrete that was as good as the Roman type but used more available materials. I don't know the current status.

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

> do you have any classic examples of bridges or buildings in continuous use for thousands of years? of course not

The Pond du Gard aqueduct is quite famous in fact.

they get stronger over time, modern capital requirements probably would not consider funding buildings that are weakest when new and only operationally stable after couple of hundred years...

https://www.science.org/content/article/why-modern-mortar-cr...

I've seen estimates of the lifespan of the Hoover Dam on the order of 10,000 years. If you left it alone some exciting things would probably happen because it's not all just concrete, there's turbines and ducts and so on, but the concrete structure will last a long time.

Non-metallic rebar (eg GFRP rebar, Basalt rebar) is also an option that's becoming more popular, though I've only seen it in low-importance structures. Both have very different design considerations than steel though: they essentially don't yield until failure loads, they have thermal expansion different axial vs radial, etc.

> time-limited construction technique

To be fair, almost all buildings, especially residential, are time limited artefacts. Even if FLW knew some of his works would become protected heritage / conservative buildings, they're still private constructions without the budget scoped for institutional buildings designed to last 100+ years. My memory is FLW already had reputation for going over budget more often than not, there was never much resources dedicated to seriously evaluate longevity of the different building systems he was experimenting with.

"The job of the architect is to spend the client's money!"

He also said:

"The surgeon can bury his mistakes; the architect can only advise his clients to plant vines."

> Steel-reinforced concrete is a time-limited construction technique. Water eventually gets in and rusts the steel.

Since you're a groupie perhaps you know and could share -- how are these concrete block homes doing almost a century after Wright started using the system described here? Are they known to have serious structural issues from rusting steel / cracking concrete? Especially because this article says "relatively unskilled labor could easily erect the walls", and because it was a new approach, I'd wonder if water would have gotten in and damaged these walls more quickly than with modern reinforced concrete (which often seems to not last long).

I'm not that much of a groupie, sorry.

A lot of FLW homes are owned by architectural or other charitable organizations, since maintaining them is expensive.

"relatively unskilled labor" -- LOL.

Not the concrete block homes, however a few decades ago they had to temporarily support the famous cantilevered roofs of Falling Water and then modify/restore its internal structure for longer-term survivability. I visited Falling Water while that process was going on and it was interesting to see how they were approaching modifying such an icon.

https://old.post-gazette.com/lifestyle/20011208lowry1208fnp3...

https://www.nytimes.com/1999/03/11/garden/an-icon-in-peril-s...

Yeah, they had a terrible time sealing the edges of the lillypad columns in the Johnson Wax building against the skylights in the ceiling.

I'd like to think that Wright had read about polysiloxane synthetic rubber compounds in Scientific American or something, and figured the building he'd designed would just have to leak until someone developed those into commercial RTV silicone to seal the roof with.

Funny, I went there on a Tuesday. They said the guided tours were only on Fridays, but when I told them I was from out of state, they said a guard would walk us around but not narrate.

It was a great office building, way ahead of its time.

I miss the days of time limited construction, nowadays residential building seems to be mortgage-life-limited. I swear nothing lasts more than 20yrs.

Would you consider insulated concrete forms (ICF) addressing the water intrusion concerns, while retaining the other benefits of reinforced concrete?

Maybe you know more about this than I do. Does the insulation last, say, 200 years?

ICF requires rebar to be dropped in the forms before pouring so... maybe not much better than standard reinforced concrete re: water intrusion.

Water could reach the rebar from the ground, but I would think waterproof membranes and proper drainage should allow it to remain mostly dry. The foam panels should also reduce the amount of air that gets to the concrete and the rebar. Of course, you want concrete to be wet for curing, but how would water and oxygen reach it after it drys out? Do you think the oxidization process will not stop after curing?

concrete is porous. IF you wrapped your concrete in a waterproof membrane, the first tear or piercing in the membrane would then become an entryway for water and there would be no way for the water to leave because of the rest of the membrane. Proper drainage is a better solution.

It's like the bridges that used epoxy coated rebar for chloride corrosion resistance and then found out that any tiny nick in the epoxy coating then causes that rebar to somehow corrode FASTER than uncoated rebar.

Does it require steel rebar or could you use glass rebar? I think most homes (that are "boxes") have concrete in compression, and not tension. That means the structural considerations for rebar are a lot lower. I think, though, as always, the lifetime of a structure is always dependent on its roof. I don't think I've seen any "multicentury" solution for roofs. Even a lead roof is only definitely good for about a century before it needs maintenance; although, it's useful for twice that long. I've got a metal roof on my house, and it came with a 100 year warranty. (The UV eventually gets to the paint, which will take out the roof.)

Copper roofs maybe? Not sure what maintenance they have to do for the roofs of Prague, but their green color is due to a copper patina.

Unfortunately you need to spend some time understanding loading on structures to understand what reinforcing is doing. Reinforcing is strictly a tension reinforcement - if the loading in compression is too great for concrete the solution is not to reinforce the concrete, it's to use a different material like steel. Concrete in pure compression is better off with no rebar at all.

Just because things fall under gravity doesn't mean they only experience compression. A simple moment frame would create tension in vertical members with only a downward load on the crossbeam creating moment.

It also would exclude the ability to do crack control in concrete with reinforcing, which would greatly lower its lifespan.

I probably don't know more than you, but I am interested in learning more about it. The insulation most often used is EPS (expanded polystyrene), which many studies are trying to find ways to accelerate decomposition from an ecology perspective. Sheltered from UV and solvents, it should last more than 200 years, with some marketing materials giving it an indefinite lifespan. We need more history on ICF, since it is a relatively new building material/technique.

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