[caskalefan]

Has anyone built a small underground home two levels high? 600 square feet would be all I need, but it would be nice to have a lower basement level to store food and my hobby, beer, because they will stay fresher, longer for extended periods of time.

I presume drainage issues might be an issue, so I was thinking about a drain the the lower level floor incase moisture got in.

My thoughts were to fabricate the structure out of cinder blocks, is this even feasible? I've searched online, but haven't really found any information on doing something like this.

 

[Wigglesdabum]

step 1 buy conex box.
step 2 reenforce the walls
step 3 bury it.
step 4 build steps down to it
step 5 build shed over top of it hiding entrance.

this is atleast what I plan on doing

 

[anickode]

Conexes can barely take being buried one deep... Not to mention 2. Ground compaction pressure gets much higher past the 8 foot (standard basement) mark, beyond the safe capacities of cinderblock. At this point you're talking reinforced poured concrete.

Water is going to be a major issue. A simple drain won't suffice. It will simply be a path for water to ger in. A footing drain and sump pump will be an absolute must, unless you're building atop a hill, in which case you can run the footing drain straight out until it intersects the grade of the hill. The problem with not using a footing drain is the risk that your sealed structure (boat) will float to the surface if the water level gets high enough. Normal groundwater isn't terribly common at 8 feet deep, but at 20 feet, it's far more likely to cause issues.

Sub-basements are tricky and expensive to build.

 

[Wigglesdabum]

no i dont suggest putting them on top of each other. But they could be put side by side. You can put 4x4s along the outsides touching the metal corners because those are reinforced.

dont trust me i literally have no experience in this. Im just brain storming.

 

[anickode]

dont trust me i literally have no experience in this. Im just brain storming.

I can tell.

I wasnt talking about burying conexes. Conexes have no business underground. I was talking about a 2 story underground concrete structure like the OP was talking about. The problem is that with no structure above ground to weight it down, a 2 story deep concrete basement can float to the surface if water isnt properly addressed.

 

[Meat Guy]

Anything can be done. Just takes LOTS of money. Your water table could be a major factor affecting the cost. The lower story would cost much more than the top story.

 

[TRM]

Has anyone built a small underground home two levels high? 600 square feet would be all I need, but it would be nice to have a lower basement level to store food and my hobby, beer, because they will stay fresher, longer for extended periods of time.

I presume drainage issues might be an issue, so I was thinking about a drain the the lower level floor incase moisture got in.

My thoughts were to fabricate the structure out of cinder blocks, is this even feasible? I've searched online, but haven't really found any information on doing something like this.

Former GC - I've built underground parking garages and structures up to 60 feet below surface grade.

Typically, on large projects, we'll use cast in place concrete, typically about 12 inches thick with a double mat of rebar.

You can use cinderblock (we call it CMU - Concrete Masonry Unit - in Vegas), but there must be adequate reinforcing steel bar, and you have to grout the cells, plus you must wait the minimum cure time before backfilling.

If you're going to go 20-24 feet below surface grade, then you need an engineer for the structure and for the hole you're going to dig (anything over 20' requires an engineer's design for trench excavation - OSHA regulations. $7,000 fine if you don't and they catch you).

Your bottom floor and your midlevel floor should be pretty easy, but your roof, if you choose to heap dirt over it, is going to require some structural engineering as well. I built a suspended slab that was designed to take 18 wheelers on it (so it was like a bridge in that aspect), and that was 12" thick with #8 bar and PT'd.

So, get an engineer. It's doable.

 

[anickode]

You can use cinderblock (we call it CMU - Concrete Masonry Unit - in Vegas), but there must be adequate reinforcing steel bar, and you have to grout the cells, plus you must wait the minimum cure time before backfilling.

So, get an engineer. It's doable.

Hell, that's probably more work than building forms and a cage and pouring. You'd have to lift every block up and then set it down over a 20' rebar, then pour concrete into the holes before laying the next course. Seems like a pretty senseless way of building a solid, reinforced concrete wall to me.

 

[Big Blzn]

I can tell.

I wasnt talking about burying conexes. Conexes have no business underground. I was talking about a 2 story underground concrete structure like the OP was talking about. The problem is that with no structure above ground to weight it down, a 2 story deep concrete basement can float to the surface if water isnt properly addressed.

Hell, that's probably more work than building forms and a cage and pouring. You'd have to lift every block up and then set it down over a 20' rebar, then pour concrete into the holes before laying the next course. Seems like a pretty senseless way of building a solid, reinforced concrete wall to me.

I sure hope you are not a contractor because some of your posts are totally out there. Concrete basements floating? Not a chance. Where do you get this stuff? Concrete basements will have major issues if water is not addressed but they will not float like a boat. Soil with a lot of clay in it will hold water and cause the concrete to shift and heave in small fractions of an inch causing cracking of said concrete. Mostly, it will cause horrible water and dampness issues of drainage is not designed properly.

As for CMU block: it is just about as strong as a poured in place basement if designed and built properly. The downside of CMU is that it is very labor intensive. On tall walls or basements you don't have to lift the blocks over the rebar. The name escapes me, (knock out CMU block, maybe) but they make a block in the 12x8x16 dimension that has open ends just for for the purpose of not having to lift the block over the rebar. The benefit of using CMU block is that just about anyone with some construction knowledge can lay block and grout themselves. BTW, you never want to grout each layer of block as you lay each row. Doing so gives you cold joints in the grouted cells and compromises the component that gives CMU walls their strength.

Cast/poured in place walls are very strong but the skill required to do them correctly is at a high level. They are a lot less labor intensive but you must do them correctly or you will have a major disaster on your hands.

With both wall types water is an issue. Proper waterproofing is a must and shouldn't be taken lightly.

All this being said, I don't see am need for 99.9% of the survivalist population to need to build an umderground bunker of this nature. Seems way overkill of just about all situations. My guess is that much of what the OP is looking for cam be done with a CMU block cabin built above ground.

 

[anickode]

Evidently you've never lived in a flood plain... Which "some" of my posts are "totally out there"? The one about not burying conexes? Or the one about how labor intensive and impractical it would be for one person to build a reinforced, filled-cell CMU wall? (which you went on to elaborate upon in your next post)

I've seen sealed concrete burial vaults with caskets inside them float up out of the ground from over-saturation. The bigger the container, the higher the buoyancy-to-weight ratio becomes.

I'm not saying that any of this WILL happen, or is even likely. I would certainly hope nobody is stupid enough to build an underground bunker in a flood-prone area.

All I'm really getting at is that one guy, digging a 20 foot deep hole and building a 2 story underground bunker from cinderblocks and mortar, and relying on a floor drain to catch and remove whatever water leaks in through the walls is 100% totally unrealistic and foolhardy.

An underground bunker without taking the proper measures against water entry is a cistern.

 

[Dragonid]

Has anyone built a small underground home two levels high? 600 square feet would be all I need, but it would be nice to have a lower basement level to store food and my hobby, beer, because they will stay fresher, longer for extended periods of time.

I presume drainage issues might be an issue, so I was thinking about a drain the the lower level floor incase moisture got in.

I've been considering something similar. Unless you're going to have a complicated pump/drainage system, or one dependant on electricity, I think the only way to make the idea feasible is to build along a hillside -- and thus receive natural drainage. The hill doesn't need to be terribly tall or steep, it just needs to be high enough to raise that second basement level above the high point of the water table.

A great location would be a hill overlooking a river/stream floodplain like this simple diagram:

With a moderately sloped ridge, the water table should drop off more rapidly than the topography. As a bonus to natural drainage, you'd get a nice view too.

 

[ShadowFlux]

my vote is keep the structure 1 story, as long as your 4+ feet underground the temperature remains constant ~58* year round. Requires less structural design and suits the same purpose. Personally I feel poured concrete will give you the best, strongest and cheapest results. Use a concrete calculator to figure how much needed, factor in rebar cost then make friends with someone who can make forms. Keep your room spans to roughly 10 feet and structural integrity from being buried is almost null issue.

As for water, you did not mention where this is. FL at sea level... need dedicated pump. Blue ridge mountains on a hill... back fill some gravel graded down hill under footer and floor slab and drainage will take care of its self.

Concrete is roughly 100 bucks a yard which is not terrible considering the permanence of what your building. Don't forget some thru holes for ventilation, water supply, electric supply, any conduit between rooms or for wall switches and lights / outlets etc. Drain plumbing for a sink and toilet. My vote is no floor drains. Apply waterproofing before back fill of soil.

Also plan out your main entrance and an emergency exit. You can use a 3' steel culvert with ladder as emergency exit in ceiling and fill it full of sand. Thus keeps you secure but if needed can open the hatch, sand pours out and you bug out of BOL.. < hope that not needed.

I have a 200 sq ft bunker with 10" concrete, currently saving up to add on due to storage space now at a premium. 400-600 should be way more than enough space for 2.

my 2¢

 

[TRM]

Hell, that's probably more work than building forms and a cage and pouring. You'd have to lift every block up and then set it down over a 20' rebar, then pour concrete into the holes before laying the next course. Seems like a pretty senseless way of building a solid, reinforced concrete wall to me.

The 20 foot lift and slide is only required if the structural engineer mandates that you have to use a continuous piece of rebar. Usually they won't (exceptions happen), and you can get by with either splicing or connectors at a more reasonable distance.

Typically, you don't need rebar in every cell, but I understand your point. We typically pour the exterior walls and CMU the interior ones where a 4 hour firebreak or concern about vehicular collision is involved - but that's underground parking garages, and not perfectly translatable to a simple two story basement.

The OP asked if he could do it, and the answer is yes he can do it that way. Is it the most efficient way? Probably not, depending on the structural design. Is efficiency his most pressing concern? Heck if I know. I would get binding estimates for both designs if I were him and make the decision.

 

[4norsemen]

Yeah, gotta agree with the one story deep plan. Going 2 stories deep runs the risk of settling , seepage, weight buckling and ladder climbing problems.

 

[choose liberty]

your underground bunker...

Im a developer and builder here in WA state....Going underground can be very tricky, and if not built correctly it can kill you. Air circulation (or the lack there of) can ruin your day. Concrete block can be unstable, and thick reinforced concrete is better, but can get expensive if done correctly.
The safest (and cheapest) underground facility is what I call a can. You can take an 8 foot to 10 foot wide culvert, cap the ends and burry it. Most are 30 feet long and some are 50 foot long for folks with families.
If burried correctly (6 to 8) feet under, it can withstand a nuclear blast so long as you are at least a few miles from the blast zone.
Im installing mine in a few months and will post some fotos as I go through the process. The can in the ground has so many benefits, I can't list all of them here. Many of them (because of their depth) don't require heat because of thermal heating from the earth. These cans would be easy to survive long cold winters without power. Even those winters caused by several nuclear blasts in the USA or even nuclear winters caused by the eruption of a SUPER volcano
Another major concerne with underground shelters is surviving ground slaps from earthquakes, nukes or impacts from celestial space bodies. Many shelters (concrete included) can't withstand these types of events. A severe ground slap will shatter most shelters killing the occupants.
NBC Air filiters are essential for any underground shelters, this will protect you against most any poison in the air. A minimum of 4 feet of dirt over head will protect you against any radioactive fall out and severe heat from fires etc, but this kind of depth has issues associated with it as you construct your shelter.

cheeers,
Liberty...

 

[Jericho]

Im a developer and builder here in WA state....Going underground can be very tricky, and if not built correctly it can kill you. Air circulation (or the lack there of) can ruin your day. Concrete block can be unstable, and thick reinforced concrete is better, but can get expensive if done correctly.
The safest (and cheapest) underground facility is what I call a can. You can take an 8 foot to 10 foot wide culvert, cap the ends and burry it. Most are 30 feet long and some are 50 foot long for folks with families.
If burried correctly (6 to 8) feet under, it can withstand a nuclear blast so long as you are at least a few miles from the blast zone.
Im installing mine in a few months and will post some fotos as I go through the process. The can in the ground has so many benefits, I can't list all of them here. Many of them (because of their depth) don't require heat because of thermal heating from the earth. These cans would be easy to survive long cold winters without power. Even those winters caused by several nuclear blasts in the USA or even nuclear winters caused by the eruption of a SUPER volcano
Another major concerne with underground shelters is surviving ground slaps from earthquakes, nukes or impacts from celestial space bodies. Many shelters (concrete included) can't withstand these types of events. A severe ground slap will shatter most shelters killing the occupants.
NBC Air filiters are essential for any underground shelters, this will protect you against most any poison in the air. A minimum of 4 feet of dirt over head will protect you against any radioactive fall out and severe heat from fires etc, but this kind of depth has issues associated with it as you construct your shelter.

cheeers,
Liberty...

http://asurvivalplan.com/utah-shelter-systems/

 

[foxkitten86]

Be VERY careful about where you buy the cinderblocks. There are apparently companies out there making them out of landfill waste and they are jam packed full of toxic chemicals.

 

[skypony38]

this is exactly what i plan on doing.

I've been reading a lot for a few years, and this method seems to be the easiest and most cost effective.... I agree with you 100% :thumb::

Im a developer and builder here in WA state....Going underground can be very tricky, and if not built correctly it can kill you. Air circulation (or the lack there of) can ruin your day. Concrete block can be unstable, and thick reinforced concrete is better, but can get expensive if done correctly.
The safest (and cheapest) underground facility is what I call a can. You can take an 8 foot to 10 foot wide culvert, cap the ends and burry it. Most are 30 feet long and some are 50 foot long for folks with families.
If burried correctly (6 to 8) feet under, it can withstand a nuclear blast so long as you are at least a few miles from the blast zone.
Im installing mine in a few months and will post some fotos as I go through the process. The can in the ground has so many benefits, I can't list all of them here. Many of them (because of their depth) don't require heat because of thermal heating from the earth. These cans would be easy to survive long cold winters without power. Even those winters caused by several nuclear blasts in the USA or even nuclear winters caused by the eruption of a SUPER volcano
Another major concerne with underground shelters is surviving ground slaps from earthquakes, nukes or impacts from celestial space bodies. Many shelters (concrete included) can't withstand these types of events. A severe ground slap will shatter most shelters killing the occupants.
NBC Air filiters are essential for any underground shelters, this will protect you against most any poison in the air. A minimum of 4 feet of dirt over head will protect you against any radioactive fall out and severe heat from fires etc, but this kind of depth has issues associated with it as you construct your shelter.

cheeers,
Liberty...

 

[skypony38]

I hope to put mine in this spring!!!

 

[caskalefan]

Thanks for all of the responses. For me, a dual story bunker is not going to be possible financially, it would cost me too much money. I would be much better off with a single story basement.