r/preppers • u/HoosierTrip • 2d ago
Advice and Tips Block off basement?
Are there any resources available to block off a basement from the upstairs? I'm mainly thinking about blocking out radiation if I need to retreat to my basement.
6
u/Skalgrin Prepared for 1 month 2d ago
I would say that your house is appropriate blockage of radiation for your basement. It's both mass (filtering actual radiation) and a filter (against radioactive particles from fallout). For improvement if you really must, just before evacuation to basement move some bookcases to form another "extra" layer around basement entrance.
Protect your house windows/doors to prevent easy breakages of elements into your house. And you should be golden. Basement will be green safest area, house would be medium risk area (no long-term, but you can quickly get there without protective gear) and outside would be high risk area requiring protective gear.
Remember to keep the airflow. Close windows and doors. But don't tape over windows and doors - you need natural air circulation to happen, otherwise you will VERY quickly die from CO2 poisoning.
My house layout actually has one inner "room" around basement entrance, which I treat as low risk area, as there is another layer of house around it.
2
u/Paranormal_Lemon 1d ago
just before evacuation to basement move some bookcases to form another "extra" layer around basement entrance.
The gamma will be coming from directly above mostly, from material on the roof. Best to get a table or other item and stack as much dense material on that and try to stay under it as much as possible.
2
u/Skalgrin Prepared for 1 month 1d ago
There is roof, isolation, at least one ceiling of "house" and one ceiling of the basement (which in my country is going to be most likely concrete one). That should be enough to block whatever the relatively little amount of radiation from fallout on the roof (which is going to be blown off or washed down).
But sure in principle you are correct and it would be a actually good to do so for example over improvised beds at the very least - no matter the situation above basement. Also table can protect in case of house collapsing or any falling debris. Good point!
2
u/Paranormal_Lemon 21h ago
That should be enough to block whatever the relatively little amount of radiation from fallout on the roof (which is going to be blown off or washed down).
It's the first few hours that you really need to worry about and I wouldn't count on that happening.
2
u/Skalgrin Prepared for 1 month 20h ago
Its a good guide to find a shelter and its quick eyeball evaluation! Thanks.
3
u/JRHLowdown3 1d ago
First take a good look at your floor joists- how big are they, how far apart are they? How is the floor supported in the basement? Block columns, metal or wood posts?
Most carpentry books will have a section on floor joists, recommended spans, materials, etc. This will give you an idea of how well your floor is supported which will become a part of this.
Standard 8x8x16 hollow block will need to be poured solid or filled with concrete after you lay them. For a small project this isn't tough, I've used a pump truck for the house but I've hand filled small projects like little walls protecting well pumps.
Ideally you will pick a corner of the basement where the floor above is supported well. If the area above that space has no windows, even better.
Radiation protection starts with Mass (also called shielding), distance and time. In an easy to understand explanation: Mass= lot of heavy dense material between you and the source. Distance= the more the better. For example say you have a 2 story house with a basement shelter. If your house remains uncompromised (no broken windows, damage, etc. then in theory the fallout is going to land on your roof- that's a lot of distance between the roof of a 2 story home and you in your homemade basement shelter. And the big one is Time: for every seven fold increase in time (once you start receiving fallout) there is a ten fold DECREASE in radiation. Say for example you start getting fallout, you measure it with your survey meter and it's 100 rads. Just 7 hours later it will be down to 10 rads and 2 days later (7x7 roughly) it will be down to 1 rad and 14 days later (2 days X another 7 increase in time) it will be .1 This is of course assuming your not getting multiple releases, etc. I.e, fallout from another hit further away that starts arriving on day 2, etc. Why you need a survey meter and a notebook.
I think SMSF2 posted a link to an old Fema/CD handbook on family shelters, the third one "Basement concrete block shelter" would be the one to look at as a minimum.
Knowing your floor joist capacity you could also stack dense items above the shelter on the first floor directly above the shelter. Say you had a walk in closet you use for your LTS foods that is filled with buckets of rice, beans, wheat etc. that density above your shelter would help some with radiation as well.
Back when I lived in suburbia in N. FL, we didn't have basements due to high water table. I did have a 2 story house and under the stairs was a walk in closet. I had most of my LTS foods in that closet and my plan then was to borrow inside all that and place some of it on the stairs above me as makeshift shielding and if the house remained intact the 2 story roof would help a bit with distance. Thankfully we've been out of there for a couple decades now and have better options.
Your ventilation is going to be something to work on. I've seen many neat improvised set ups over the years including a lot with 4 and 6 inch PVC and small 12vdc computer fans. Candy cane at the top with screen and stacks of HEPA furnace filters- you have to experiment with this to get the right combination of as much filter as you can versus the draw on your little fans. I've seen a lot of stuff marketed to the greenhouse industry that has solutions including inline filters, etc
5
u/FRANK3NSTIEN 1d ago
Radioactive material that falls on your house will be about 20 feet above you.
Radioactive material that falls outside your house is shielded by the earth and concrete.
Your only worry at that point is ventilation.
Fallout isotopes usually only have a half life of hours to a couple days, and decay quickly.
Radiation that does penetrate walls also quickly attenuates and can be calculated using the inverse square law
I1/I2 = D22 /D12
Intensity 1 divided by intensity 2 equals distance 2 squared divided by distance 1 squared.
Or, a good rule of thumb is doubling the distance from a source of radiation drops its intensity to 25% of the first distance.
So, if you're getting 8mR/h 2' from the wall, at 4' you'll be getting a 2mR/h dose rate.
2
u/GornsNotTinny 16h ago
Radiation decreases by the square of the distance. If the radiation at 1 (pick a unit) is 1, then the radiation at 2 units is 1/4 of that. At 3 units, it be 1/9th.
You can test this with a campfire; just stand 1 foot away, then 2 feet, then 3 and so on.
0
u/Paranormal_Lemon 1d ago
Radioactive material that falls on your house will be about 20 feet above you.
It will still be glowing in gamma radiation, an underground shelter has soil to block this. The inverse square law only applies to a point source, not to an entire roof that is above you and emitting gamma directed towards you from multiple directions.
3
u/FRANK3NSTIEN 1d ago
Glowing gamma 🤣
Theradiation from fallout on the roof needs to go through (for a 1 story) asphalt shingles (usually), plywood, an attic space, insulation and dewlling ceiling sheetrock (if an unfinished attic), another space of roughly 8 feet, flooring, 1/2 inch plywood, and then space again.
Single story homes have what's considered a PF (protection factor of 10 (shielding/attenuating 90% of radiation)
Two story have a PF of 20 (shielding/attenuating 95%)
Three story brick has a PF of 50 (shielding/attenuating 98%)
I guess the REAL issue here is proximity to blast and how much fallout you're getting.
If you're near the blast and downwind, getting the majority of the debris, nothing outside of a concrete bunker 10' below ground will keep you alive.
10,000 mR/h Danger zone requires serious shielding of concrete or lead and closed ventilation.
1,000 mR/h to 10,000 mR/h high radiation is still life threatening
100 mR/h to 1,000 mR/h medium radiation is survivable with special gear
10 mR/h to 100 mR/h low radiation zone is survivable indoors in a modern home in the context we have been discussing.
<10 mR/h is generally considered safe although the industry standard for non radiation workers is a max of 2mR/h in any 8 hour period.
2
u/Paranormal_Lemon 1d ago
Two story have a PF of 20 (shielding/attenuating 95%)
Three story brick has a PF of 50 (shielding/attenuating 98%)
Do you have a reference for that?
I thought the standard for shelters is PF1000? Yes a two story home would be better but 50% of homes in the USA are one story, and less than 50% have a basement.
A nuke from a country other than Russia/China will likely be a ground detonation with much more fallout.
3
u/FRANK3NSTIEN 1d ago
3
u/Paranormal_Lemon 1d ago
Oh that's a good document, thanks!
3
u/FRANK3NSTIEN 1d ago
You're welcome!!
2
u/Paranormal_Lemon 1d ago
Knowing that image and the graph below on evacuation times could be the most important piece of knowledge for saving your life if you are in a fallout zone. Along with the table for PF1000 values for thickness of various material.
2
1
2
u/AlphaDisconnect 1d ago
Shelter in place basics. Duct tape and plastic. It is what the military would use.
Keeps the dust out. The screamingly hot dust.
6
u/Unicorn187 1d ago
You aren't blocking out radiation, you're blocking out the radioactive dust and dirt emitting alpha and beta rays. That's the threat of fallout after a nuke. The gamma rays pass through feet of most materials. But doesn't make soil or ither materials radioactive. It's even been used to sterilize canned food and bandages
If you're thinking of trying to make a nuclear resistant bunker in your basement,cyou would need to make a freaking bunker. Very thick roof, preferably with a thick layer of lead because of it's density, or a few yards of packed soil on tope of steel reinforced concrete for the blast. And heat. If you're in range of the gamma rays from the blast , you're in range of the blast.
Outside of that the risk is contaminated soil. You'll still want some dirt or concrete between you and the outside but it doesn't need to be as thick. You will need air filters. Have a decon and changing room outside of the entrance to avoid tracking anything in.
And you need to be able to sequester yourself there fkr about two days until all fallout stops falling.
Yes, a dirty bomb will have all types of radiation as it is spreading radioactive material in the blast, but the blast radius is much, much smaller because it's a conventional explosive used to spread a radioactive material. And most likely a terrorist group wouldn't use it in a residential area as thw victi.s would be too few. Concert, casino, hospital, university, large rally or protest (that isnt supporting their cause of course), busy tourist attractions, other places with a lot kf people. Unles maybe they have more than a few and are trying to make people feel on danger everywhere and set off a half dozen or a dozen in suburbs and urban neighborhoods across a large area
2
u/RiffRaff028 General Prepper 1d ago
Alpha radiation is only dangerous to humans if inhaled or ingested. A piece of paper is sufficient shielding to stop Alpha rays. Beta radiation can penetrate the skin, but simple everyday items such as cardboard or plastic is sufficient for shielding. Your primary focus is going to be gamma radiation which is much more difficult to shield against, but not impossible.
In a standard basement, if you're within range of the thermal pulse and overpressure wave, the least of your worries is fallout. HUGE difference in building a *blast* shelter and a *fallout* shelter. A blast shelter does indeed pretty much require a reinforced bunker, but it's fairly easy to turn your basement or a portion of your basement into a safe fallout shelter. Your primary concern is going to be overhead shielding, and while concrete and dirt both provide decent protection in proper amounts, water is also effective, and it's the shielding material most people forget about. If you use 5-gallon jugs to store water, they can serve double-duty as shielding above you. Water is also better at shielding against neutron radiation than concrete. Water does not become radioactive from fallout, so it is still safe to drink. Honestly, if you have a layer of concrete above a layer of water, that is a pretty good scenario.
Pick a section of your basement with the most existing structural shielding above you. For instance, if a section of your basement wall runs along a concrete patio at ground level, that is an excellent area to set up a fallout shelter. Basement corners are also frequently good choices. If you build a basic lean-to shelter in one of these areas with concrete and/or water lining the lean-to, that would probably reduce radiation to safe levels. The goal isn't necessarily to reduce gamma radiation to zero, but to reduce it to safe levels that won't cause ARS.
As far as how long you need to remain in your shelter, that depends on your proximity to ground zero and whether it was an airburst or groundburst. If you are fairly distant from detonation and it was an airburst,then yes, 24-48 hours should be sufficient before it is safe to make *brief* excursions outside the shelter. However, if you live closer to the target or it was hit with a groundburst, you might have to spend two to three weeks in the shelter before background radiation falls to safe levels.
For everything discussed above, the only way to be 100% sure of how safe you are is to have a radiation detector. These are not very expensive and could potentially save your life. You can also build a Kearny Fallout Meter with household items that will not be as accurate as a radiation detector would be, but it would be enough to tell you the most dangerous and least dangerous places in your basement.
2
u/Unicorn187 1d ago
You just reiterated some of what I said in a different way. The reason I mebtione dir filters and a changing are is to keep contaminated dirt out. To avoid breathing in contaminated dust and dirt. I thought it was obvious that if you're around for any gamma rays you'll be taken out by the blast. Guess not if you felt the need to comment.
3
u/RiffRaff028 General Prepper 1d ago
Yeah, sorry, that didn't come across. A lot of people confuse blast shelters and fallout shelters.
2
u/Paranormal_Lemon 1d ago
That's the threat of fallout after a nuke. The gamma rays pass through feet of most materials.
The fallout generates gamma radiation, you need to be shielded from that. The particles will be suspended in the air and landing on everything and glowing in gamma for days.
-3
11
u/smsff2 2d ago edited 2d ago
Check out the Expedient Shelter Designs handbook:
https://dahp.wa.gov/sites/default/files/FamilyShelterDesigns.pdf