Looking to have about 40 inches of dirt overhead or so.  Trying to just get a gauge for how think the roof and floor slabs will need to be and what kind of bracing support I'll need.  Looking at a 10' x 10' room or larger if cost is reasonable.

Movie room...riiiiight

that's great....first thing I thought of too.

If I were doing it all over again, I would make my garage floor out of spancrete, and have the lower level "movie room" accessible from the basement. Probably have a Ft. Knox in-swing vault door to keep the kids from getting in there and messing around with fancy a/v equipment.

 

Maybe he is going to make snuff films?

I hope so

Once the walls are up, you have several options. Spancrete or a similar precast plank (like they use in 2-story motels) is an option, but it'd be a small order, and thereby expensive.
You can also set corrugated steel floor decking, and then pour it with about 6" of concrete. It may need some steel channel or small I-beams every 4' or so to support the weight. Best bet, especially with the additional soil load, is to have an engineer or architect run the numbers. Or just build it 3x stronger than good sense tells you to..... But I'd have a pro size it if'n it was me.

Another thing, I've never been involved in a construction project in Texas, but I know that many areas of your state have expansive clay soils that move enough when wet to destroy conventional basements. If you live in such an area, you should have the whole thing engineered.

Or you may be able to buy a giant septic tank, or something similar, and just bury the whole damn thing, but you'd have to figure out how to get in and out.

But whether you build it or buy it, probably the most difficult part will be getting it successfully waterproofed. Again, assuming you live where that's a factor.

No good answers from this keyboard, but food for thought. Hope it helps.

And enjoy your movies  

EDIT:  A 4" thick floor slab should be good at the bottom. No less.

Well, I need something to tell the concrete mixer when he asks why he's dumping 5 yards of concrete into a 12 foot deep hole.

Already got the girls picked out or do you plan on a snatch and run?

Shouldn't this be in the Movies and Home Theater forum?  

I don't know, should it?

Purely inanimate objects bro...think stuff like long term food storage.

Can you tell us a little more on how you plan on building it? I am asking because 40'' of earth is going to take some pretty good supports. Are you dead set on a 10'x10' room or can that change? How do you plan on insulating this from the ground temp to keep condensation from forming? I guess the easier question is what's your budget for this? How long do you plan on staying in the watching movies?

Something to keep in mind when building like this is how many cubic feet you have inside a shelter......I mean movie room. Each person in there will need at least 105 cubic feet of fresh air every hour. If they do not get that, the moisture and CO2 levels reach a very uncomfortable and even dangerous level. Also, you do not have the full amount of cubic feet in the shelter because you have people, food, chairs, bathroom, and anything that takes up space, takes away from reserve air inside the shelter.

So a 10' x 10' x 8' shelter has 800 cubic feet of air. If just one person is in there and nothing else, he can live for about seven and a half hours before things start to get uncomfortable.

I myself like to have at least a 12 hour reserve of air when I do something like this for someone. This way if everyone falls a sleep, it isn't forever.



Let me just give you an idea of what you can build as far as a Monolithic dome goes, and you can compare the cost, and benefits between the two different structures yourself.

Let's build a dome that is 20' x 10.5' like the one in the link below.
Here is what we know about it. It has 314 square feet on the floor, and 660 square feet over the dome. I figured it out, so trust me it is 660. For volume inside is has 2255 cubic feet.

Cost to build:
Airform.............................$2138
Concrete in the dome............$800  8 yards @ $100 yard, but I would mix my own for about $50 a yard.
Rebar..............................$700
Foam...............................$2500 Contracted out, if you can do it or you have a buddy do it, it is $1100 or less.
Floor................................$1000
Total................................$7138

To finish it off the inside, and do it right, I would say another $1500 max, but that doesn't include the movies or NBC filters and pumps. It would be a real liveable area or man cave with a real bathroom and small kitchen. You have room to build an over head storage area with ten foot high ceilings. I would probably do the bathroom different as this is a shelter just so you have more room in it. These figures do not include digging the hole or any septic, but you need to do that with anything you build, so I am assuming you know that already.

Now, if you wanted to build a 24' dome, that would cost you an extra $1800, but you go from 314 sf to 452 sf of living area, plus you are at almost 3000 cubic feet of air volume inside.

http://shop.monolithic.com/products/20-x-10-surplus-airform

http://shop.monolithic.com/products/construction-drawings-dl-2002

Pictures of what it would look like inside.
http://www.monolithic.com/stories/io-20-1/photos


When you are done, you have something that can survive this below. Read the fourth paragraph down.
http://www.monolithic.com/stories/iraq-mosque

And survive this...for a while anyway.
http://www.monolithic.com/stories/testament-to-domes-strength

Actually, my point is the strength factor. You do not have to worry about how deep you have this underground, unless you plan on going deeper than 30 feet. Then things need to be changed and beefed up.

I've been thinking about building one for a while. If you are going to do it, my advice is to make it withstand a 5 PSI overpressure. Roof about 3 feet think with rebar every foot. There are books available that give the details.

Electric and communications companies set precast vaults all the time. The elec vaults will sometimes be in three pieces. The floor with a wall section (4' or 5' tall) is set, then a strip of butyl rubber is placed around the top for the next wall section to squish into place (keeps water from coming in between the sections. Then the same butyl rubber stuff for the top to sit on. I've never seen water come into the two that I've been inside. Regarding water, they all set a sump pump. Many have an open, drive-over rated grate that rain comes in through. So water-proofing is still possible without that open grating. The comm companies spend more money to keep the water out, obviously because of the electronics. They are actually air conditioned.
It takes a decent sized machine to do the lifting.

I'd look into one of the precast septic tanks and do a manhole (womanhole) for access. Fewer people might be interested if it's just a concrete truck driver, but he's going to tell other people just like everyone else will. But he might forget where you live.

good post

This is not the kind of thing you should guess about. Pay a few bucks and get it properly engineered. The plans should not be real expensive.

Yes, 5 psi would be as low as I would go.

These domes are designed to with stand 2000 pounds of force per square foot. That is almost 14 psi over pressure. They can take much more than that, but they were looking at an F5 tornado when they designed them.

A 300 mph wind puts out a force of 404 pounds per square foot or 2.8 psi over pressure. That over pressure with the safety factor of 5 times that puts us around 2000 pounds of force psf. Also keep in mind that the dome is curved both horizontally and vertically, so the full force of any wind can never be fully realized against its side because there is nothing for the wind to grab. The wind just keeps slipping around the dome.

Now take a conventional home with a flat wall that is 8' tall and 40' long. It has 320 sf of area exposed to wind. A 300 mph wind hits it and that wall has to hold back 404 pounds of force per square foot. That comes to 129,280 pounds of force against that whole wall. Good luck with that. Once that wind hits the wall, it will go up until it hits the eve and the roof will lift off and all structural integerity is gone at that point and every wall blows away.

As far as stopping flying objects, I think we covered that in my last post, but here is another way of looking at it, and testing it that may be more in line with the way people on here are thinking.
http://static.monolithic.com/thedome/bullet_test/index.html

And another that went through a Califorina wild fire.
http://www.monolithic.com/stories/vista-dhome-the-home-of-dr-and-mrs-al-braswell/photos

Read this about earthquakes and the last paragraph about a home running out of heating oil in Alaska when it was -30. They didn't know it for two days until they ran out of hot water. These are insulated beyond anything built today. Also there is a church that is 8000 square foot in Alaska and it costs them $72 a month to heat.  
http://www.monolithic.com/stories/war-bonnet-construction-alaska

You will NOT find a safer, a greener, longer lasting as these last 100's if not 1000's of years, and a more maintance free home anywhere in the world that can be had by the average person. You won't.

40" of dirt huh? Perfect for block gamma rays.

Sorry guys for taking so long to respond, was up about 29 hours for work, had to sleep it off for a few hours.

Anyway, this movie room will be on my mother's property in West Texas.  I'm currently in the DFW metroplex and HOA covenants would prevent me from doing anything cheap or quietly where I live.

For DFW, I'd agree on 5 PSI, and probably more since the area around me is peppered with potential DGZs on some Russian's targeting computer, but it's a little bit of overkill for Marfa.  But it very easily could be in a fallout footprint from El Paso depending on the winds and dirt is cheap (but bracing and support may not be).

As far as budget, my reason for posting was to get an idea for cost and allocate from there.  Primary purpose would be for out of sight storage of long shelf life foods (so temperature moderation is important), secondary purpose would be a shelter.  1_BIG_BUNKER, thanks for your post on this and giving me a cost guideline.  Do you guys work in West Texas?

Oh yeah, 10' x 10' was just a guideline.  If it's cost effective to scale up, I will.

You need to pay an engineer to design it, 40" of dirt is HEAVY. One bucket load from a 980 loader weighs 20-24,000 lbs., a dump truck load weighs 43-45,000lbs, about what will be on top of your "movie" room.

Quite interesting.

There was a thread a couple months ago about a guy in Utah that dug a huge hole in the ground next to his house, built a underground movie room, exercise room, "storage" room, and the whole thing connected via underground tunnel. On top he a built a nice garage.


Anyone remember this thread?



Gene

I do remember it.  I also remember thinking that the guy had a lot more scratch than I do.

This one?  Oh yeah, don't look if you get jealous easily...

Bunker

Yep, that's it.


And yes, he had some $$$ in that project. But it sure came out nice.

Why don't you email me and we can talk about this on the phone. I have a couple of large dome projects going on at this time, but building bunkers is my first love. I would be more than happy to help you out for just a few GOOD beers and some GOOD food.

I ran into this problem when pouring the floor for my "root cellar" a month or so ago. The bricklayers I had along knew what was up and went along with the ruse. The concrete guy didn't act like he believed it, but was agreeable. Kind of like he had done quite a few of them in the past... he knew what was up. Probably gonna have him pour the roof too.