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I'm exploring a post-apocalyptic world and want to build a realistic scenario for the condition of abandoned ruins. What would you estimate to be the lifespan of the following building types? And by lifespan, I mean the upper limit on usability as a structure. Obviously, they would be in bad condition (that's why they call them ruins after all), but usable means that they offer shelter and reasonable structural integrity (i.e. they're not in immediate danger of collapse).

  • steel frame skyscrapers (10+ stories)
  • reinforced concrete buildings (1-10 stories)
  • masonry/brick buildings (1-10 stories)
  • wood-frame small buildings (1-3 stories)

Professional materials science or civil engineering perspectives would be super appreciated :D

EDIT: On further thought, I've broken up the "reinforced concrete and/or brick" category into separate categories as I think they may be substantially different in their lifespan.

EDIT 2: Let's say that we are talking about a temperate region, roughly approximate to the US mid east coast (e.g. Virginia). Decent amount of vegetation but not rainforest. Slightly above average precipitation and humidity.

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    $\begingroup$ Former architecture student here: You are missing a very key aspect to your question. What environment are the buildings in? Nature is what degrades buildings, and the environment changes everything. The great pyramids are thousands of years old and would actually be in much better condition if not for people literally stealing the bricks for other buildings, same for the Colosseum. In contrast, Angkor Wat is just as much a wonder of construction despite having been built only a few hundred years ago, much younger by comparison. That said, the jungle has completely ravaged the site. $\endgroup$ – TitaniumTurtle Dec 20 '18 at 14:54
  • $\begingroup$ So to clarify your question with modern construction in what I'm assuming was once a dense city. Where is the city? Is it next to the ocean where the salt water mist might cause rust? Is it in the desert where sand storms continually smooth surfaces like near-literal sand paper? Is it in snowy mountains where the cold will embrittle the supports and the weight of continuous snowfall caves roofs? $\endgroup$ – TitaniumTurtle Dec 20 '18 at 15:00
  • $\begingroup$ Thanks for bringing up that good point. I've added more detail which I hope clarifies. Let's say it would be like somewhere in Virginia. Maybe even D.C. but that doesn't mean I'm specifically thinking about that location, I'm just putting it out there for purposes of guiding the discussion. So... close to the ocean but not coastal. $\endgroup$ – T Nguyen Dec 20 '18 at 15:03
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    $\begingroup$ worldbuilding.stackexchange.com/questions/36140/… $\endgroup$ – Separatrix Dec 20 '18 at 15:13
  • $\begingroup$ Possible duplicate of What happens to an empty, modern city? $\endgroup$ – cobaltduck Dec 20 '18 at 16:23
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Happily, many instances exist where we can pinpoint the date of disaster and abandonment of structures. You can get a good idea of how relatively modern structures and cityscapes will appear after 30, 50 or 70 years:

Chernobyl disaster: Pripyat

WWII disaster: Oradour sur Glane

Extrapolation into the Future: Life After People

Or simply tour the abandoned structures in Detroit (USA): Houses in Detroit Theatre in Detroit

Unattended wooden structures can survive a long time if well & sturdily built for decades. This house in Pennsylvania has literally looked like this, unpainted and seemingly unattended, for at least the last 40 years. Some of the external laths have fallen off, but it appears otherwise sound.

Concrete & steel structures, as you can see from Pripyat, survive well in the first few decades after abandonment. Even with no maintenance, most urban structures would have a "usable lifespan" into the century mark if not longer.

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    $\begingroup$ This is a good answer but the part that I don't find quite tenable is the projection of current deterioration rates, especially in regards to steel and reinforced concrete. Pripyat is probably the best real-world evidence we have of the deterioration of abandoned modern buildings, but I don't think we can say "Look, they're not so bad after 30 years so that means that they can survive well past a century." I would imagine that deterioration isn't linear due to oxidization of steel... $\endgroup$ – T Nguyen Dec 20 '18 at 16:14
  • $\begingroup$ ...There must be a critical mass of deterioration where structural supports start to fail and place greater stress on remaining supports leading to a snowball effect. It could well be that modern structures are reasonably usable for 50 years and then collapse pretty quickly. $\endgroup$ – T Nguyen Dec 20 '18 at 16:16
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    $\begingroup$ That's why I also provide the link to "Life After People". As for my answer, I only speculate as far as "the first few decades" -- clearly, we have evidence that such structures will be "usable" within that time frame. The series in question specifically looks at modern structures (and infrastructure) going out from 50 to 100 to a 1000 or more years. $\endgroup$ – elemtilas Dec 20 '18 at 16:17
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    $\begingroup$ Basically, I think "usable lifespan" within a post pockyclyptic scenario would be in the 0 to 20 to 30 year range. A post disaster society will probably be building new structures of its own (log cabins, stone cottages, etc) by the time any modern buildings become structurally unsound. $\endgroup$ – elemtilas Dec 20 '18 at 16:20
  • $\begingroup$ Cool, I haven't had a chance to check out that video yet, still at work. I'm looking forward to watching it later. I've also found a good book in my research, but it's a little expensive, en.wikipedia.org/wiki/The_World_Without_Us. $\endgroup$ – T Nguyen Dec 20 '18 at 16:32
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The estimates for steel and steel reinforced structures in the "Life after people" series seemed to be around 200 years. Without continuing maintenance, the steel corrodes and breaks, allowing gravity to pull the structures down.

Now this figure will change according to circumstances. In wet climates, moisture will accelerate the corrosion process, while in dry climates the steel will last much longer. Other external stresses may factor in as well. A building in an earthquake zone will be subjected to forces from the earthquakes, but without repair, the damage will become additive and the structure will collapse in subsequent tremors. A building in the wildfire zones of California may suffer fire damage, and the structural steel may lose enough temper to allow for collapse (much like the World Trade Center towers on 9/11).

So your story can provide specifics, like the tower collapsed in the earthquake of 2111, but I would guess that steel and steel reinforced concrete structures might last 200 years on average.

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Stone structures can last effectively for ever if they're constructed with thick walls, as the Wikipedia list of the oldest buildings demonstrates. Effectively all of the listed buildings are of stone.

I can't find any sources for the other materials listed, but as far as I'm aware wooden structures, if treated correctly, can last for hundreds of years if not damaged e.g. by storms.

As far as I know we don't really have much evidence to tell how long concrete takes to naturally erode, since these structures tend to be less than 100 years old.

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  • $\begingroup$ The Colosseum and the Pantheon were built about 2000 years ago, and of concrete. So, there's one way of looking at it. (Mind you, their concrete recipe was different than that used in modern times.) $\endgroup$ – elemtilas Dec 20 '18 at 15:35
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    $\begingroup$ @elemtilas Not only was the recipe different, but they were not steel-reinforced, which is a significant distinction. The steel inside reinforced concrete has a much shorter lifespan and its relatively fast deterioration would decrease the lifespan of reinforced concrete. I specifically mentioned reinforced concrete in the question because my focus is more on modern (present time) buildings. $\endgroup$ – T Nguyen Dec 20 '18 at 15:37
  • $\begingroup$ @TNguyen -- Right. Forgot to mention that! But your question doesn't focus on ancient concrete, which is why I mention the ancient structures here only in passing, specifically re the length of time for concrete to significantly erode. $\endgroup$ – elemtilas Dec 20 '18 at 15:41
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The lifespan of buildings strongly depends on the climate that they're in. Are they in the desert, withered by the sand, are they close to the ocean, where the salty and wet air would attack the steel, or are they in a climate with a lot of rain which could slowly wash out the structures? or maybe high temperature differences which stretch the materials? In general you could say that especially concrete and steel frame buildings would last for ages, surely several hundred years, given they're not in a harsh enviroment. Those are buildings made to last. And they would. Wooden buildings are more interesting, but they're also depending on the climate. Dry wood can last very long without weakening in structure, while wood in a wet climate would rot in a few decades.

EDIT: now that the climate is specified I can provide a better Answer. For concrete buildings it stays the same, and for wooden buildings i would give them around 30-50 Years, based on my observation around the places i lived. Water is a huge factor here, if the roof stays intact, the structure will survive longer, if it's damaged, the building can rot away within 3 years.

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  • $\begingroup$ "especially concrete and steel frame buildings would last for ages... Those are buildings made to last." All evidence points to exactly the opposite, which makes me think your answer isn't based on any real evidence or science. $\endgroup$ – T Nguyen Dec 20 '18 at 20:50
  • $\begingroup$ Now I'm curious: What evidence tells that they do not last? In the example of chernobyl, all the structures are still intact. The windows and interiors are broken, gone or severly damaged, but the buildings itself last. $\endgroup$ – miep Dec 20 '18 at 20:54
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    $\begingroup$ theconversation.com/the-problem-with-reinforced-concrete-56078 "Early 20th-century engineers thought reinforced concrete structures would last a very long time – perhaps 1,000 years. In reality, their life span is more like 50-100 years, and sometimes less. Building codes and policies generally require buildings to survive for several decades, but deterioration can begin in as little as 10 years." $\endgroup$ – T Nguyen Dec 21 '18 at 3:27
  • $\begingroup$ fastcompany.com/3037370/… "...new concrete structures constructed in urban coastal regions using current code requirements may degrade prematurely and require costly maintenance over their service life" $\endgroup$ – T Nguyen Dec 21 '18 at 3:30
  • $\begingroup$ linkedin.com/pulse/… "While some [concrete] buildings will last for more than 50-60 years without problems, some will start developing problems after few years of construction." $\endgroup$ – T Nguyen Dec 21 '18 at 3:32

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