Digging out basement floor

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12-05-05, 07:00 AM

Jason

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Digging out basement floor

My homewas built in 1918, its a 2 1/2 story colonial with ballon frame construction. My basment floor is paper thing and bulged in some areas. I want to repair it but also dig down a couple inches so my head doesnt hit the steam pipes on the ceiling. How thick should or does the new floor need to be and is it ok to dig down to the bottom of the foundation or is this going to cause other problems. I will be doing this work myself.

Thank you, Jason

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12-05-05, 07:17 AM

marksr

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Minimum thickeness for concrete floors is usually 3.5" You can dig the floor deeper but if you dig lower than the footer you will need to address the footer. My grandfather had an old farm house that had less than 5' height in the cellar [also had stone foundation and dirt floor] What he did was dig it out to an acceptable level, pour concrete [extra thick at the perimeter] and then block up past the stone. You probably won't need to do anything that drastic but you will need to shore up the footer if you dig below it.

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12-22-05, 10:26 AM

sullijim

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Same problem

Hi Jason,

I have a very similar situation with my house. It's 80 years old and the basement only has a 6' ceiling.

The floor is poured concrete but has cracks and holes that allow water to seep up when the water table is high.

The basement walls are poured concrete and seem to be in good shape.

I would like to know how to go about breaking up the old floor and digging it 2' deeper.

If anyone has any ideas of what's involved as well as an approximate cost I would be very grateful for the information.

Thanks,
Jim

Last edited by sullijim; 12-22-05 at 10:41 AM.

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12-22-05, 12:18 PM

Concretemasonry

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Digging out basement floor

Before you remove an entire basement floor, keep in mind it is one of the things that is preventing the wall and footing from sliding into the basement.

Some old structures may appear to be very stable, but all it takes is some moisture to increase the lateral wall loads and provide some lubrication.

When I put in drain tile, I left a portion on the floor in place until the adjacent floor slab was poured on top of the footing and against the wall.

If you are digging deeper, this is more important, but you can put your floor against the footing instead on top of it - the deeper you go, the more side pressure. Just make sure you have everything braced.

Dick

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12-22-05, 03:44 PM

sullijim

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Digging Basement Floor

Thanks Dick,

I don't know how far below the floor the footers go but my guess is not much lower. My concern is as you mentioned, if you knock the floor out and dig down to or below the footer what happens to the house. How would you support the house while you dig below the footer and how do you reinforce the footer once you've dug below it?

Thanks,
Jim

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