Your thoughts on my basement plans

[EddieWalker]

Eddie
How thick is your slab for anchoring?

It's just a standard 3 1/2 inch thick floor with rebar on 2 foot centers in both directions.

How would you guys attach or build an above ground shelter on an existing concrete slab?

 

[EddieWalker]

Eddie
How thick is your slab for anchoring?

It's just a standard 3 1/2 inch thick floor with rebar on 2 foot centers in both directions.

How would you guys attach or build an above ground shelter on an existing concrete slab?

 

[CurlyDave]

If I had to put it on top of an existing slab, I would pour a second slab about 8" thick on top of the first one and accept that there will be a step up into the shelter. The idea is to make the shelter weigh enough that it won't be picked up and blown away. I wanted to really overbuild, I would go 15" and make two steps up.

This lets you embed L-shaped rebar into the newly poured shelter floor.

To tie it to the existing slab, make up some pieces of #4 bar that look like giant staples. Drill into the existing slab and epoxy these into the existing slab, so that each one has two ends anchored. If you do this you can use the tops of the staples to support the rebar grid in the new slab.

Before you pour the new shelter floor, clean the existing slab very well and paint it with one of the acrylic bonding agents intended to make a new pour bond to old concrete.

 

[farmer2009]

It's just a standard 3 1/2 inch thick floor with rebar on 2 foot centers in both directions. How would you guys attach or build an above ground shelter on an existing concrete slab?

I wouldn't want to try and tie it to an existing slab. I'd saw cut the slab and remove that section of concrete. Then excavate down for a 12" floor. Drill and epoxy rebar into existing slab, build new grid and stub up rebar for walls. Form walls and roof for a single pour.

Seems like a seen that somewhere about a professional company. They pored walls and roof at same time (monolithic) so they weren't relying on mechanical fasteners to hold it together. But I can't remember where. Thinking they poured the walls, roof and footers all at once, then added a floor later inside. They were adding storm shelters to existing garages.

 

[GPintheMitten]

There's a video on this site about anchoring their steel shelters in a garage. I know you want to build your own but it might give you some ideas for anchoring and tying new concrete structure to the ground and to your existing slab. It sure looks like a good way to anchor.

Valley Storm Shelters | Superior Storm Shelters, Tornado Shelters, Safe Rooms

 

[BitChin1]

It's just a standard 3 1/2 inch thick floor with rebar on 2 foot centers in both directions.

How would you guys attach or build an above ground shelter on an existing concrete slab?

Eddie take a look at this design guide detail from FEMA - might help answer your question

Link

 

[Streetcar]

Eddie
Your existing slab is too thin to serve as foundation for storm shelter.

Curly Dave has a good plan. The only thing I would add is to roughen existing concrete before you place the new slab.
Your other option if you want a flush floor is to remove existing slab and pour new foundation.
I would pour the walls of my shelter and use the walls to support the roof. You will need to have the L shaped bars from the top of wall into your roof

 

[BitChin1]

Eddie take a look at this design guide detail from FEMA - might help answer your question

Link

And here is the FEMA publication that goea along with the above guide (link shows access denied, but still appears to work for me)

Link

 

[Deere Dude]

I would cut the existing floor, dig down 8" and put rebar across the floor and put the ends into the existing floor for a little more weight and strength and maybe a little more leverage against a strong wind..

Then weld 8' rebar, or as high as you want the ceiling to each of the lateral floor rebars. I did one this way and also put heavy cattle panels to make a heavy mesh all the way around the wall and on the ceiling.

I would pour the floor and when that is dried I would form and pour the walls on a different pour, preferaby 8" minimum.

When the wall is dry I would use plywood and form a ceiling panel and brace it in which to pour an 8" ceiling on. I would have cattle panels and rebars across the ceiling welded to each of the vertical rebars to tie everything together. Put a couple small roof vents on each end, I used 4" PVC and works well. Don't forget to run electricity and an outlet inside.

 

[Streetcar]

Jj

I would cut the existing floor, dig down 8" and put rebar across the floor and put the ends into the existing floor for a little more weight and strength and maybe a little more leverage against a strong wind..

Then weld 8' rebar, or as high as you want the ceiling to each of the lateral floor rebars. I did one this way and also put heavy cattle panels to make a heavy mesh all the way around the wall and on the ceiling.

I would pour the floor and when that is dried I would form and pour the walls on a different pour, preferaby 8" minimum.

When the wall is dry I would use plywood and form a ceiling panel and brace it in which to pour an 8" ceiling on. I would have cattle panels and rebars across the ceiling welded to each of the vertical rebars to tie everything together. Put a couple small roof vents on each end, I used 4" PVC and works well. Don't forget to run electricity and an outlet inside.

Structurally, the rebar should extend from the foundation into the wall with a bent bar (L shaped). The same thing for the roof.
Why use cattle panel instead of rebar?