Above ground TORNADO shelter

Need to build an above ground concrete tornado shelter.  

What about getting a 2000 gallon or larger concrete septic tank made with a doorway in it.  Set it upside down on a slab and cover most of it with dirt?  Might even put an entrance way a few feet long with a roof over it to protect the door.  I'm glad I live in a place where tornado's are rare!

How about a CONEX box or SEACAN ?  They are steel on 6 sides..  A small one is 20 ft long and 8 ft wide... Maybe they have even small of some sort... Set it on the ground and push dirt up 4-5 ft on the 3 walls to help stabalize.. You can cut into the steel for a vent, etc.. Big doors on one end.. Bolt one shut and modify inside/ outside latch for the other ??

Edited by steve(ill) - 09 Dec 2020 at 1:00pm

I think one of them containers could be made into a nice shelter a lot cheaper than biulding one.

Conex boxes do not do well buried, Sides cave in as not designed for Side loads just Edge loads.  Know of two purchased and set onto Concrete slab with footer, then forms and rebar added around with support braces INSIDE at two foot intervals concrete poured and allow to cure before removed bracing.  When poured Cover Top laid Styrofoam on the top and sealed edges, forms set to side walls, bracing installed top to bottom and pour completed.

There are fellows around here that used to build cement dome houses. I was in one west of Lacona Iowa years ago. They look like 5 or 6 coffee cups turned upside down joined together by doorways. These domes were about 12' across at BBC the bottom. One of these would make a great storm shelter. I think they were called geodesic dome homes.

Havent really had to test it but we buried a conex container. I had a deep ditch not far out the back door, so I dug one side out enough to sit it in. Put rock and drainage tile around it, put a culvert along the ditch side, covered the whole thing with roofing tar and a layer of tyvek and made a doorway. Then pushed dirt over the whole thing. 10 years ago or so and still holding up fine.

Might look up a video they had on This Old House - PBS - as they had a show on then and building them . One was free standing on a cleared lot - said house was gone, as much of neighborhood was now rebuilt but this structure was still standing and family was safe because of the shelter . 
 Showed a crew building one inside a garage area , all poured concrete with rebar skeleton , vibrated concrete during pour and roof or top closure  was rodded to sidewalls over a poured form . So full unit was poured over large plywood box form but also onto foundation that was designed to not yield in a direct hit . 

Call me crazy, but having been in three different tornadoes in my life, Above ground / tornado shelter don't belong in the same paragraph let alone the same sentence. Not me,it's either the southwest corner of the basement or a regular old storm celler.

Mobile home parks (tornado targets) here in MN are required to have storm shelters and they seems to be concrete with earthen berm as easiest and cheapest form of construction to meet code . 
Now it seems if your out in rural area a simple means would be a large oval concrete culvert section with enough dimension to be used for other purposes also . This could be sunk down into side hill or just at lower elevation so as to not look like a eyesore in the front yard .   

used to be a family here that made concrete grain storage bins, the son made his house out of several of the bins connecting them with arched walkways, his dad made his 2 car garage out of one, had a walk door and a large overhead door. they hunkered down in the garage one evening when a tornado went thru, all walked out just as good as they walked in, everything outside was ripped up! he has since passed and the son sold the farm place they lived on, but the house and the garage are still there and look just like they did when constructed. i was in the garage one day, seems the walls were about 8 inches thick.

Precast companies here have been producing septic sized shelters with a hatch style door as the old homes used to have for cellars. Require the boxes be anchored and then earth nested to keep them
In place during a event.

BUTT, BUTT, BUTT... you didnt answer felici question.. What about the scaffold ?