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-   -   Want to fill old hot tub hole in basement. (

konacj 08-01-2013 11:15 AM

Want to fill old hot tub hole in basement.
I've got an 11'x10'3"x2' hole in my basement from a previous owner who wanted to install a hot tub of sorts. It's concreted on the sides and bottom.
I want to fill the hole and lay a concrete slab on top so I can put down carpet and have a regular room instead of a room with a hole.
What should i fill the hole with?
Sand, gravel? A mix?
How thick should my final slab be and do i need to support it with rebar?
The rest of the room is concrete.

joed 08-01-2013 01:19 PM

I would fill it is stone and pour a 4" slab on top. A few rebar pins into the existing floor will keep the new slab level if the stone settles underneath. I have also seen this done with no fill underneath. Build a platform with plywood on top and pour the slab. Rebar pins are required for this option.

konacj 08-01-2013 01:25 PM

How is best to set those rebar pins? Do I drill into the concrete below and simply place them, or do they go flush on the concrete as it lays?

stadry 08-01-2013 01:27 PM

bank run or washed gravel would be my choice,,, you should place the fill in compact'd ' llifts ' ( layers ),,, i'd choose 6" lifts depending on the suitability of the mtl :yes:

rebar adds flexural strength to the patch but not compressive strength,,, consider installing #4 horizontal bars grouted into drilled horizontal holes into the existing slab,,, i'd also install a vapor barrier under the conc ( on top of the compact'd fill ),,, that's almost 7cy of fill + 113sf of 4" conc,,, it'll deep you out of trouble for several days :laughing: place the new floor at the same thickness as the existing floor.

good luck !

Maximus275 07-09-2015 07:56 PM

How do I backfill old concrete hot tub with out taking out an cap it with 4in. Cement to match existing patio slab

joed 07-10-2015 07:19 AM

Two year old thread.

stadry 07-10-2015 08:47 PM

but its yesterday's inquiry,,, same way - fill w/gravel & mix bagg'd conc to be 4" thick,,, you can't match existing UNLESS you overlay the whole slab :thumbsup:

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