So the nuclear apocalypse happened, and 90% of the population died from the either the blast, radiation, famine, violence or disease within the next 5 years. Fortunately, the United States government planned for this eventuality, and built subterranean dwellings, in which people would be protected from he hellfire above. The plan was for these shelters populations to emerge and start rebuilding the world, and to help America heal its radioactive wounds. My question is, what materials would be needed to build a city in he post apocalypse?


• The location they are building in is San Francisco, which was hit with 30 megatons during the war.

• They need to be able to power this new community

• They need to be self sufficient.

•They have 500 years to build

•The City doesn’t have to have the same population as before, just a small settlement with electricity will do.

  • $\begingroup$ If you want to rebuild on the site of 30-megaton nuclear attack, the first step will be cleanup. $\endgroup$
    – Alexander
    Commented Apr 9, 2018 at 21:45
  • $\begingroup$ Materials shmaterials. You didn't say what's the deadline. At one end, all you need is flint and timber and some 10,000 years. At the other end you need cement, gravel, machinery to mix them, fuel for the machinery, construction equipment, fuel for same, rebar, copper wire, steel wire, glass, asphalt, machinery to grade the roads, fuel for same, bricks, timber, mining or drilling equipment, fuel for same, pipes of various sizes, welding equipment, fuel for same, lighbulbs, electric generators, fuel for them, sheet metal, metal and wood working equipment, tools, tiles, paint, adhesives, ... $\endgroup$
    – AlexP
    Commented Apr 9, 2018 at 22:11
  • $\begingroup$ @AlexP's point is very well taken. Trying to rebuild a modern Earth city of population 50,000 including utility infrastructure and shipping/transportation infrastructure within 10 years is MUCH different than building it within 300. But that might not matter. I feel this question is too broad. The amount of equipment and material necessary to clear and rebuild to a modern tech level is astronomical. Remember, SF was founded in 1776. It's had 242 years to get to where it is. As the time shrinks, the equip/materials list increases exponentially. $\endgroup$
    – JBH
    Commented Apr 9, 2018 at 22:36
  • $\begingroup$ What do you need? Obviously: the same things that we needed. $\endgroup$
    – RonJohn
    Commented Apr 10, 2018 at 0:43
  • $\begingroup$ You might want to read the book Lucifer's Hammer which is all about people in california surviving an asteroid impact and preserving civilization, most of what they do will work just as well for a nuclear war. $\endgroup$
    – John
    Commented Apr 10, 2018 at 15:32

5 Answers 5


Weaponry used in the war

Firstly the question is how 'dirty' the weaponry used in the war was, as anything other than clean bombs (https://en.wikipedia.org/wiki/Nuclear_weapon_design#Clean_bombs) or something like pure fusion wepaons (https://en.wikipedia.org/wiki/Pure_fusion_weapon) would result in many years of residual radiation and radioactive particulate. The radioactive particulate in particular can be a problem as it deposits and becomes embedded in the soil, effectively ruling out effective horticulture (Ie. The environment may be relatively safe to traverse but it would be a bad idea to dig up the soil for any reason)

Beginnings of Settlement

Assuming that the population in the subterranean dwellings also has a stockpile of equipment and resources (machine fuel, generators, etc) then the first step is the acquisition of resources essential to survival.

  1. Water - An effect of nuclear fallout is a vast reduction in precipitation rates due to dust in the upper atmosphere (~45% reduction - http://academic.evergreen.edu/z/zita/articles/SciAm/GW_CC/NuclearWar2010.pdf) therefore it will be essential to bore deep ground water wells and check regularly for radioactive contamination.
  2. Food - Since the soil will most likely be still contaminated, the safest way for production would most likely be something akin to greenhouses or buildings containing hydroponics basins and modified uv lamps. Depending on meteorological conditions and the nature of the nuclear weapons, there may be significant solar dimming or cold resulting from dust. Most of this however should have settled in 5+ years.
  3. Shelter - The ideal would be to use the subterranean complex for the first generation of settlers, as this will provide ready made shelters as well as established infrastructure. Also there will likely be very little wood available for construction as a result of fire, low light conditions, and low temperatures etc. New trees will be not be suitable to cut as plants bring radioactive material from sub-soil to the surface, and cutting them could therefore expose humans to extra dosage of radiation. Quarried stone will most likely be the best and most readily available basic building material as it will be the least affect by radioactive fallout

Advancing from Basic Settlement

Once the basic elements of food and shelter are setup, establishing infrastructure to service the needs of the population will be important. For the first 500 years, there will be bountiful supply of metals to be reclaimed, smelted and reused for tools and infrastructure improvement.

  1. Workshops and Fabrication - Initially a number of high volume workshops will be needed to fabricate everything from tools, to pipes, to struts, moving part mechanism etc. This will allow for work on the other projects to advance
  2. Water - Water will need to be distributed first from a central point (eg. well(s)), however as the water needs of the populace rise a distributed system of pipes will be needed. Pressure to push the water around the system will have to come from either high elevation reservoirs or water towers.
  3. Waste - One of largest factors in the extension of the human life expectancy was the toilet. Getting excremental waste away from the places where humans will eat and sleep will prevent disease and parasite proliferation.
  4. Roadways and logistics networks - As the settlement grows, it will become vital to be able to move people and goods around in a safe and efficent manner. Roadways and thoroughfares will have to be established, as well as methods for the movement of goods (Teamsters, delivery persons etc)
  5. Power - Assuming there was no portable nuclear reactors etc stored for this eventuality (and the skills to safely use them), then the only viable means to generate power will be kinetic based renewable power generators. Solar panels will not be viable as it is a complex industrial process to create even minimally efficient photo-voltaic solar panels. The most suitable power sources will be hydroelectric and wind powered generators as these are relatively simple to construct and materials will be readily available for construction
  6. Schools - While one of the lesser immediately important pieces, having a existing knowledge base to begin with is a huge advantage in getting started, but more importantly to prevent knowledge degradation, a school system coupled with an apprentice type system will be vital to ensure the preservation of knowledge especially around complicated technology and processes
  7. Policing - Inevitably, with any larger population, some degree of criminality or behavior that infringes on the freedom of others will occur. Establishing early a system of fair assessment of crime and punishment will be important to preserve the necessary happiness and productive societal attitude (ie. Widespread lawlessness and infighting would destabilize the population to the point of self-destruction)
  8. Culture - As the settlement advances and becomes more populous, a cultural identity and formal structure for creative arts to flourish will provide happiness and sense of identity to the society, which is an important basis for the settlements longevity.

500 Years represents about 15 generations (based on a 33 year reproductive cycle - https://isogg.org/wiki/How_long_is_a_generation%3F_Science_provides_an_answer) which given there inst very harsh environmental conditions or defense worries to contend with, and given that there was a reasonable stockpile to get stated with, there would be reasonably good chance of success.


Modern technology needs lots of people and lots of resources. Food is especially important. You need a large food surplus combined with a large population to get the many many specialists needed to support modern technology.

  1. You need a lot of people in the shelter or away to attract outsiders. Retaining key knowledge like doctors, engineers, and scientists will greatly speed up rebuilding.

  2. You need to pack as much agricultural technology and seed stock into your bunker as possible. The ability to plow, dig wells, irrigate, and manage soil will be essential.

  3. Lastly you want to have as much technological information stored as possible, possibly as books. The faster they can require the knowledge base for technology the faster they will recreate it - if they have to reinvent electricity without knowing about it it will take forever.

  4. A number of geiger counters and other radiation sensors will also help all the planning will be ruined if they try to settle in a radioactive valley.

The simplest way to generate electricity will be a water wheel driven generator so including some steel and copper to make building on earlier will also help. If they have to mine the copper it will take a lot longer.


First off would be basic tools, whatever goal you want to achieve ultimately whether high-tech or medieval. Hammer, axe and saw as well as seeds for planting might form the basic tools and items you need.

If you can include books for survival as well as medicine then your settlers would have a good chance to survive. They can hunt, scavenge, learn, farm and build.

I think the big question would be the radiation. Water would be contaminated and the soil as well. Depending on how much of the Earth was savaged by the war and being that your settlers/survivors are building in SF, they might not have good resources. If your world allows for it, maybe radiation removal tablets or powder can be used to remove it from a small area or so. Alcatraz might be a good place to go to as well for a good place to defend from marauders and maybe far enough from the main nuclear strike that it has pockets of clean soil.


Based on the events of Hiroshima, fallout from those 30 megatons specifically wouldn't really be that big of a deal. Many residents were living within a stones throw of ground zero within 6 months of the detonation. Healthy, not likely, but definitely not lethal. You would be much worse off depending on if a nuclear reactor was nearby however. So depending on the integrity of the shelters the government provided, you could just wait out the fallout, ala... Fallout.

Now in terms of rebuilding, that's a little harder to quantify. I could make a laundry list of things you would need: medicine, materials, etc. However, one thing that is a known quantity, is modern living. If I recall correctly, under ideal circumstances (ie, our world right now), modern living requires a bare minimum of at least 2 million people to function. It requires this number simply to be able to man all the various jobs required. This obviously includes readily accessible resources, which may not be the case if you went for a Resource War as a cause of the apocalypse. So without a higher level of automation, or an abundance of salvaged material, anything resembling modern life as we know it would be, full stop, impossible without more manpower.

The time required to reach a suitable population level to sustain this level of living would be determimed by how inhospitable San Francisco is in your scenario; something that is not really easily quantifiable without going into detail of a specific example.


Q:what materials would be needed to build a city
A: anything. everything. Mud, steel, concrete, wood, PCV, Glass, irrydium.

Only one criteria. Well two:

FIRST plane cannot be poisoned/inhabitable.

SECOND knowledge on how to build things.

500 years is longer than USA existed as a country and look how it changed.
500 years ago was 1518. things we needed to discover between that year and now include electric, engines, mass production, industrialization, atom powered submarines, combine-harvester, GMO and sliced bread.

There is nothing that could stop people to make things from anything. Especially when you already have the knowledge so you just take thing A, mix it with B in C proportion and voila! Glass wool.

500 years is too much to not do anything. There are/were buildings that didn't last that long. Mountains crumbled to the sea, lakes dried out and people still had time to die in wars and it was just a quarter of century.

Shorten the time to 5 years and then you will have Realistic setting for such question.


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