Exactly what it says on the tin: what would an above-ground residential apartment designed to negate the effects of a one-kiloton nuclear surface burst at 500 meters look like?

NUKEMAP-2 says that the effects of a 1-kiloton surface burst at 500 meters are:

  • an overpressure wave of approximately 4.2 PSI

  • thermal radiation of approximately 29.3 joules per square centimeter

  • ionizing radiation of approximately 5050 rem

In addition, take into account the fallout produced by such an event: at 500 meters, that's somewhere between 1 and 1000 rads per hour, depending on the wind.

By "functionally negate", I mean that when the detonation occurs, the occupants of the building may or may not (presumably, they will) notice but will be functionally safe from ionizing radiation (I know some small measure of it will get through no matter how much shielding there is), as well as unharmed by any blast/thermal effects, as well as safe from the maximum-possible 1000 rads/hour of fallout for approximately a week.

By "above-ground", I mean that, aside from a single basement level, the structure is above the ground.

The building has 150 apartments in it.

What would an apartment building, built to withstand this look like? Preferably, it's skyscraper-style, but I can understand how that might make nuclear defense difficult.

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    $\begingroup$ What is it housing? There are very different basic considerations that have to be addressed depending on what the building is being used for when it isn't being exploded at that will drastically alter how it is built. $\endgroup$
    – Ash
    Sep 12, 2021 at 1:27
  • $\begingroup$ @Ash Residential building; will edit for clarity. As an aside, have you noticed that questions related to nuclear detonations seem to be disproportionately popular? $\endgroup$
    Sep 12, 2021 at 1:41
  • $\begingroup$ The question doesn't specify what volume the building has to contain or what its purpose is (warehouse, housing, etc.). 5 psi overpressure is about equivalent to a 163 mph wind (cdc.gov/niosh/docket/archive/pdfs/niosh-125/…) which isn't unmanageable but the less height the structure has, the better. $\endgroup$ Sep 12, 2021 at 1:42
  • $\begingroup$ Thanks. Not particularly but I've been here a lot longer so I've seen all sorts of trends come and go. $\endgroup$
    – Ash
    Sep 12, 2021 at 1:42
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    $\begingroup$ The closest thing I can think of would be a WWII German Flak tower, re-adapted to be used as a fallout shelter. It wouldn't be very comfortable as a place to live, but a good place to evacuate to ahead of a nuclear strike. youtube.com/watch?v=6jgvkzD8d3k $\endgroup$
    – DWKraus
    Sep 12, 2021 at 17:59

3 Answers 3


You are looking at a piece of real estate that was specifically built with the expectation of taking a hit, the building is simply too expensive to justify if you don't have a reasonable expectation of it being nuked, and has several rather odd and expensive extra features that you'd never bother with (mainly because of the fallout not the blast):

  • It will look like a piece of brutalist architecture somewhat akin to the lower portion of the Torre Velasca in Milan shown below, with a heavy concrete facade broken by minimal, deepset windows, the panes will be thick, lead doped, antiradiation glass with inbuilt wire mesh to reinforce them against blast pressure. I include external windows on the assumption that the building code is either outdated or utterly stupid and requires them. They do have aesthetic benefits and not having to light the storage corridor is a saving but the building would be more secure without.

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  • There will be only one ground floor entrance with heavy but narrow front doors and an anteroom that blocks direct movement paths to dissipate blast pressure in the event that they are open. The whole front lobby area of the building can be isolated by internal blast doors in case of excessive contamination and alternate through the building used instead.

  • The walls will be built with more reinforcement than is strictly necessary and will incorporate a Lead baffle layer to prevent radiation penetration. There will be a sacrificial thickness built in to the outer structural elements of the building that can spall off when exposed to the thermal shock without compromising building strength.

  • The building will need blast shutters and a closed circuit ventilation system, not to deal with the initial blast, although the shutters will be handy if they can close fast enough, but to keep the fallout at bay.

  • Internally people will not live/work exposed to the windows/external wall of the building, a corridor will separate the outer skin of the building from the lived-in spaces with a solid internal wall, this corridor is purely a maintenance/storage space. Primary access into the living spaces will be through a central elevator and stairwell shaft core. The outer walls may become radiation saturated over time is this air gap is useful regardless of whether there are windows in the outer wall or not.

  • The building will be as short as possible and will not expose any vital functions on it's roof space. The ceilings will be low, 2.5m(~8ft) or less, to keep the floors as small as possible. The ventilators, water tanks, etc... that would usually grace the roof line of an apartment building are either in the basement or concealed in a top floor engineering level under the protection of a heavy roof.

  • External links are hardened and put as deep underground as possible. No satellite uplinks, all communications data will come in over hardlines, preferably fibre optic because it's less effected by radiation than metal wires are. The water pipes etc... will be buried deeply across the city and the service branches will come into basements from below the foundations of buildings so they provide the shielding that would otherwise be lessened by decreased depth.

Given that the building is being designed to take a hit it is probably being built to take more than 1kT, most strategic weapons are much larger. Again fallout is more of an issue than blast due to the persistence of those effects.

GrumpyYoungMan has noted that the ventilation system will need to supply the building on a completely closed circuit for at least 50 hours with heavy scrubber capacity for around 100 days. I would suggest that it will actually be rather larger per the fact that 1kT is a rather small blast. Further he has noted that the lead baffle is rather inefficient and that a water jacket would give as much protection from the initial blast and could then be pumped out, through builtin decontamination sprinklers, to lessen the ongoing effects of the post blast contamination and fallout on the building making Lead-lining unnecessary, I'm not 100% sold on this as I'm not sure how heavy the jacket would need to be, and thus the structural requirements, but it is an idea worth exploring.

  • $\begingroup$ Comments are not for extended discussion; this conversation has been moved to chat. $\endgroup$
    – Monty Wild
    Sep 15, 2021 at 14:09
  • $\begingroup$ "like a piece of brutalist architecture somewhat akin to the lower portion of the Torre Velasca in Milan" I very much doubt it // it's got to deal with an air blast from an unknown direction so round with thick, solid & smooth outer walls containing as few windows or other openings as possible is very strongly mandated by the brief that's been given // which wouldn't look anything like that. $\endgroup$
    – Pelinore
    Sep 20, 2021 at 11:37
  • $\begingroup$ @Pelinore Round buildings are inefficient of space use requiring them to have more exposed surface area, especially roof space, reducing resistance to over pressure. $\endgroup$
    – Ash
    Sep 21, 2021 at 6:15
  • $\begingroup$ Space efficiency isn't exactly the priority & if an air blast above is a possibility you'd use a dome for the same structural benefits to the attack as the circular walls provide for the surface blast the question actually talks about, if you're really expecting that blast a flat surface that will fully absorb the entire blast rather than allow some to slide off is more than likely when engineers have things like wind tunnel tests available to show the effects of a blast on comparative flat & curved surfaces. $\endgroup$
    – Pelinore
    Sep 21, 2021 at 7:08
  • $\begingroup$ @Pelinore A dome is even less efficient and a residential apartment block is in a city, space is at a premium you do need to be concerned with using it efficiently. $\endgroup$
    – Ash
    Sep 22, 2021 at 5:34

One-kiloton nuclear surface burst at 500 meters is not that bad

From the blast wave perspective, it does not look as bad as a category 5 hurricane - and residential buildings in some municipalities, like Miami, are already built to withstand that. Of course if the charge detonates closer, or it is more powerful, then the situation would change, but if we strictly follow the requirements in question, then everything is good.

The light flash and ionizing radiation are more difficult to deal with. Granted, they are easy to deal with if the building has no windows - but this is residential building, so I assume that having windows without permanent shutters is an implied requirement.

Penetrating radiation can be dealt with by utilizing heavy metals in glass composition. It is also possible to filter out most of infrared light. Negating visible light flash is probably the most difficult task, and I am not sure we can get 100% secure protection here. There are "smart" dimming glasses, but I am not sure they can act fast enough to prevent eye damage if someone would be looking from the window straight into the nuclear fireball.

However, there is one good solution to the windows issues. If our building is designed as a courtyard, rather than a tower, the windows facing the courtyard will be safe. Granted, without usable windows on the outside inhabitants will miss the views, but at least we can have both safety and windowed apartments.

Radioactive fallout is also a manageable issue. We need to make sure that the building has central ventilation system that can be switched to adequate filtration, and people won't be able to open windows in their apartments.

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    $\begingroup$ This was going to be my answer and I found this sweet image. I hope you dont mind me adding it. This is a little tactical nuke; 1/15 of the bomb dropped on Hiroshima. Evacuation distance standing outside from 1000 pounds of TNT is a little over 500 meter so inside a building you should be ok. The fix for the windows is to have them all above eye level, higher on the wall. Or have them be glass brick or darkened glass. $\endgroup$
    – Willk
    Sep 12, 2021 at 17:35
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    $\begingroup$ Maybe I'm being dim, but surely 1000lbs is much less than 1000 tons? I believe a US ton is 2000lbs. $\endgroup$ Sep 12, 2021 at 18:30
  • $\begingroup$ A kiloton is 33 of those semi-trailers listed at the bottom of your sheet as requiring 2100M clearance. That is so bad. $\endgroup$ Sep 12, 2021 at 22:21
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    $\begingroup$ As far as I can tell, this answer did not mention anything about 1000 pounds of TNT until @Willk edited that image in. It doesn't seem to be the original author's fault that this answer is incorrect. $\endgroup$ Sep 12, 2021 at 22:53
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    $\begingroup$ Ug my bad. Those decimals. I see it has been reversed. Sorry all. $\endgroup$
    – Willk
    Sep 13, 2021 at 0:08

An octagonal concrete wall will some decorations on it, but no windows. It may have some cameras to allow residents to look what is happening outside. The light for the apartments would come from the courtyard in the centre. If the ratio of the base size to the height is big enough the external perimeter wall won't have to be too thick. To reduce the sense of confinement the roof would have to be a well furnished terrace.


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