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Covering an old basement

Covering an old basement

Covering an old basement

(OP)
Working on a job where the Contractor wants to just pour a new slab over an existing basement. The building is about 100' long, but about 30' of it has a basement. The current slab is beat up, and they want to pour a new topping slab. I am fine with that over the existing on grade, but the basement they want to just cover up. Supports needed aside, what problems do you see enclosing a basement?

RE: Covering an old basement

It's a waste, for one.

Even if you converted it into an unused, unheated storage area it would have some utility

Aside from that: concerns about mold in a damp dark unconditioned place, something or someone getting into it, and sprinklering it (if required)

Either way, you need some kind of supports over the top of the basement whether it is abandoned or not. I can't imagine you would just backfill it.

When I am working on a problem, I never think about beauty but when I have finished, if the solution is not beautiful, I know it is wrong.

-R. Buckminster Fuller

RE: Covering an old basement

(OP)
Well, thats my point, it would be totally of limits, no access, just a void. I would like them to fill it in, and be slab on grade just like the rest of the building.

RE: Covering an old basement

When the contractor's brother's best friend's ex-wife disappears the cops will insist that all fresh concrete work be demolished to have a look underneath.

RE: Covering an old basement

If the existing structural slab is just covered up and the basement underneath remains unused, it is unlikely that the structural slab will be reviewed and maintained properly in the future. Eventually it will deteriorate to the point it could become a significant liability, not to mention you are adding additional superimposed dead load to the structural slab by adding the topping.

Jackhammer the slab, drop the debris into the basement. Follow with lifts of compacted granular and then pour new slab-on-grade.

RE: Covering an old basement

(OP)
Thanks. Hopefully they will go that route.

RE: Covering an old basement

Architectural/safety issues aside, it doesn't bother me structurally. Nor from a durability perspective assuming that everything is concrete.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

RE: Covering an old basement

If the basement is all below grade, I would have no problem with just filling it in as suggested.

However, if there are some daylight walls, there may not be enough reinforcing in the wash to take the lateral load from the compacted fill.

Mike McCann, PE, SE (WA)


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