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Discussion Starter #1
I'm posting this to get ideas for my underground bunker. I am a welder so I have decided to go the steel box route.
1-I will be building it myself.
2- I want it to be 8' tall x 8' wide x 12' long.
3- Will be using 4'x8'x 3/16" sheets. Trying to decide on the reinforcment ribs, either 3" channel (4.1 # ft) or maybe square tubing on 24" centers. Not sure what size tubing would be of the same strenghth. Or would I need larger channel??
4- Need to figure out a design for strong secure entry hatch. Second entry would be drainage tube big enough to crawl through, just in case.
5- I would like to make an elevated floor ,about 18"-24" with removable floor panels for storage underneath.
6- Still need to figure out about ventilation.
Also as said I will be doing this myself, secrecy is golden it seems. So I will be building the unit in sections and lowering them into the hole and finish welding them together down there. I still need to figure out a good rust proofing method. Was thinking about using the same type tar that you paint on basement walls defore you backfill. Any thoughts??

Also might run power from closest place to bunker for electric to run lights,dehumidifier etc. Still need a back up system though. Thinking solar??

Have well on property so a way to get water if electric is down is on my mind also.

Planning on burying this thing under 24" dirt.

All ideas are invited as I have never built one before. But that has never stopped me in the past.

Thanks
 

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wouldnt it better to get shipping containers and add to them?
I think 8x8x12 is way too small.
drainage - I would be really concerned with drainage...
Ventilation
power
 

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I would look into a "Hi-Cube" 20' Container (9'6"H X 8'W x 20'L) Reefer Unit - it would have Ventilation Passages Built in, Insulation already installed. Then Build a False Floor for your needs. If you get a Unit labelled "Cor-Ten", it will have a very Robust Anti-Corrosion feature already built-in! I wouldn't Bury it more than a few inches deep - maybe just enough to have a garden or grass cover. You will need French Drain/Sump Pump to keep interior Dry (Along with some sort of Ventilation).

If you get Lucky, You might find one with an Integrally Mounted But Remote operable), Multi-Voltage (Three Phase Generator!) Diesel Powerpack, and Refrigeration Compressor Unit.

Expect to pay about $3000 for a good Container, and Who Knows about the cost of the Powerpack. If you find a "Thermo-King" Powerpack that is Twenty Years or so Old, it is really a Mercedes 240 D Engine, and parts are still available.

You will have to engineer a Foyer/Entry.
 

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Getoffmylawn, sounds like you and I have some very similar ideas(see my post "structural input" a few lines down the forum). I had thought about reinforcing with tubing and someone pointed out it would be difficult to rust proof the inside of the tubing. I saw a shelter online the other day that had a door with two ways of opening. Slide to enter or exit, or drop on hinges to exit if blocked. Of course there wasn't any close ups to able to reverse engineer. I'm still thinking out the entrance. Having a toddler stairs would be easier for him to access, but a ladder would take up less room.

Good luck, and please share what you come up with.
 

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Getoffmylawn, do a search on here on undergrounds/shelters/bunkers, there are already many threads that you will find VERY helpful!!! You didn't mention what you are planning this shelter for, is it just for storms? For a long term SHTF???

I'd like to comment on just a few things as I have never posted about our underground in here before.

Yes, don't have only one entrance/exit unless you absolutely have too, always have an alternate exit and try to have at least one that opens 'in'

Try and have more than the 2 required air vents incase one gets blocked.

On running power or using generators, if you are truely in a SHTF, there will be no power and if you are hiding, there is no way to run a generator without it allerting others to where you are.

Our entire UG was DC powered utilizing a 'peddle power' generator to recharge the batteries for running the lights, fans and the pump from the well, a very simple system with no problems since 1990. Having an inverter is great too, it allows some power for things like communications, recharging batteries, etc.

Really give alot of consideration to sanitation and how you plan to deal with it, we were lucky to be able to have a toilet run to the existing septic system, but we planned on using the 'bucket' method if that fails.

Yes, proper drainage is a must, we had one member who ended up with 3' of water in hers after a severe storm, not fun at all!!!

I belong to a very large group who have been putting in UG's since the 80's and we have learned from each other what works and what doesn't, one of my friends is currently putting in a 24' x 48' shelter, and all I can say is wow, that is more room than my house, can't wait to see it!

We are currently planning a storm shelter that we can access quickly thru the Mobile Home we live in since we are in a tornado prone area but it will be a simple one made with block or poured concrete, no bells and whistles, so like you, I will be looking at all these posts too for improved ideas, and yes, we will have an alternate exit just incase, one lady was recently stuck in her shelter for 3 days cause she couldn't get out!!!

PS: The tar that is put on basement walls is for basement walls hahaha Do some research or take the recommendations of others about rustproofing products.
 

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8'x12' under 2' of soil is a total load of 21,000 lbs @ a 110 lbs per ft^3 soil weight (average).

That means your maximum moment at the center of the 8' span is 880 lb-ft (moment). The deeper the roof members the more moment they can resist.

What this means is even if the members are 1"x6" steel tube, they will perform better than a 3"x3" steel tube because they have more depth and can resist the bending moment more efficiently. The only concern will be twisting because of how thin they are. So make sure you weld the top decking to the joists across the span, and not just the ends. It will act like cross bracing between floor joists in a house.

Look in to underground fuel storage tanks. That will give you a good idea of the robustness required to bury a round metal structure.
http://www.engineeringtoolbox.com/fuel-oil-storage-tanks-dimensions-d_1585.html

Lastly be careful, I do not recommend building a steel underground shelter, but like the shipping container crowd you seem dead set on doing it.
 

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One of our group in New Zealand buryed 2-40' shipping containers and used filled old tires around the entire structure before backfilling. Have no idea if this would indeed help with side bowing, just thought it might be worth mentioning???

Thanks Name for mentioning how much dirt actually weighs, thru the years I have heard of 2 containers that the roof began to bow in, even with all the reinforcements they did, guess it wasn't enough!

Live and Learn...
 

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Discussion Starter #10
Thanks for all the replies and good ideas.

Thanks NAME for the dirt weight info. I can get whatever size tubing or channel I need to make sure it does'nt start to bow. I had also thought about concrete, but that would take the hidden & secret build away. Plus more expensive and time consuming.

Beaniemaster2, the dual vents is a good idea I had'nt thought of. But you can't have too many. Will deffinetly have 2 ways in........and out. The bunker I plan on using to hide out if SHTF. It will be close to my house so at night I can recon if necessary. For drainage I figured 3-4' clean rock with drain tubes around the bunker. I plan on pouring about 60 -80lb bags concrete for the foundation. The sanitation & alternate power are still two things I am trying to figure out. Solar is one option with bunch of batteries?

Parrothead, I originally thought about a hatch with a ladder for the main entrance and also a side hatch, but smaller as a backup exit. Now I think I am going to just make it like a walkout door under heavy camoflage. Which means I now have to engineer some type of door that can take a beating if need be. Already have some ideas, won't be quite as strong as a blast door but you would have to have a torch or dynomite to get in. It will open out, but the entry way will protect it from falling trees. i figur at least 3/8" thick, with solid 1" frame for reinforcement. just have to come up with a latch.

Handload, I looked into containers, but with the initial cost, and then the cost of the steel to reinforce it, I think I can build cheaper. Not as big, but cheaper and totally secrect as I will do all the heavy lifting myself. No cranes, plus I don't think a crane could get back in where i want to put it.

But as always, the ideas in my head are always changing and nothing is written in stone yet. The input from here will help me sort it all out for sure. I appreciate all the ideas and the threads on where to look. Thanks!
 

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Always have an emergency exit on the opposite end...Even if only 2' diameter pipe it will help...
 

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Spraying with a bitumin based coating will reduce moisture standing against the metal, but you need to get soil moisture away from the walls. The best way to do it to insulate the walls with rigid foam, then lay polyethylene outside. Outside that fill the gap between the structure and soil with gravel. It's best to dig a trench at least 12" deeper than the structure base along the outside of the excavation. This way the rubble trench carries water down below the base and away from the structure. Be careful to not tear the plastic when filling the trench and keep a little extra plastic than needed at the top as it will tend to pull down as you fill the trench. It's better to allow it a little creep than to tear it by holding to firm at the top. This method is quite effective. Just remember the order: Wall, coating, insulation, barrier(plastic), rubble, soil.

Polyethylene will last for decades if not exposed to sunlight. It helps to extend a water barrier horizontally away from the stucture 50% farther than the structure is tall. Bury the barrier no less than 2' at the highest point and lay it with constant fall ( 1" per ft is fine) away from the structure. This is called a "rain skirt", but it could be better described as an umbrella when used with an underground structure.

Hope some of this helps you.
 

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If you get a Unit labelled "Cor-Ten", it will have a very Robust Anti-Corrosion feature already built-in!
Just want to point something out here... Cor-Ten steel is a special alloy that develops a rust patina to protect it from further corrosion AS LONG AS THE ALLOY ISN'T IN CONSTANT CONTACT WITH WATER.

Cor-Ten is known for rusting out very quickly when in constant exposure to direct, trapped moisture.
 

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Maybe consider earthbag building? You could build curved bows that keep dirt away (like a retaining wall) and provide outer storage... Space for good french drain... and you could put beams across.
 

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Discussion Starter #17
Hello again.

After searching on the web for a good way to keep rust from attacking this thing, I ran accross this website : http://sanchem.com/ox.html

After reading about it ( NO-OX-ID A SPECIAL)and getting thier info it sounds like a possible way to go. Has anybody here heard of this stuff? I am waitng to hear back from them on some key points about thier product. But sounds easy to apply, relatively cheap and not too bad of sq. ft. coverage. If anybody wants to read about it more I guess I could post the PDF file on here? Then it could just be downloaded. Any and all input appreciated.
 

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Hello again.

After searching on the web for a good way to keep rust from attacking this thing, I ran accross this website : http://sanchem.com/ox.html

After reading about it ( NO-OX-ID A SPECIAL)and getting thier info it sounds like a possible way to go. Has anybody here heard of this stuff? I am waitng to hear back from them on some key points about thier product. But sounds easy to apply, relatively cheap and not too bad of sq. ft. coverage. If anybody wants to read about it more I guess I could post the PDF file on here? Then it could just be downloaded. Any and all input appreciated.
An anti-corrosion grease does not seem like a good choice for ground contact. It sounds GREAT for above ground saltwater corrosion, though.
 

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I used a shipping container as a form for concrete poured around the container. I prefer to encase the steel in concrete, that way it will last forever, of course 3/16s steel would take a long time to rust through. I placed stairs inside the container for ease of getting into the storm shelter and carrying supplies. Also, stairs are better if someone is elderly or injured. Think it through, if you can plumb in water, elec, and a drain if you have enough slope to open end a drain. At the end of my drain tile, about 150 ft away, I place a barrel of gravel for the water to drain to. The barrel wil inhibit roots from trees or bushes from seeking the drain.

http://www.survivalistboards.com/showthread.php?t=160378&page=4
 
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