3,000 lb new point load on existing slab

[Jmeng1026]

A client wants to remove some walls and install lvl beams to open their floor plan up.

The point load on a column on the 1st floor would support a 3,821 lb load.

This will have to be transferred down to a column in the basement which will sit on an existing concrete slab. Assumed 4" slab but unsure. Assumed 2,000 psf soil bearing capacity.

I'm assuming the slab should be cut and a 2'x2' (12" thick) concrete footing should be poured and then the slab fill in but does anyone have any other suggestions?

Could a steel plate be placed on top of the existing slab instead of cutting the slab? If so, what thickness and what length and width?

Thanks for the help.

 

[XR250]

Might want to have the contractor drill the slab first to see if it is thickened. Short of that, I would cut a footing of the appropriate size. 24x24 seems excessive for that load but need to check the load on the current basement column too.

 

[EngDM]

Depending on your post size, and what fill is under the slab, you might be able to engage enough of a bearing surface below the slab without needing to cut anything out. Worst case you dig out the slab as you mentioned, leaving the existing reinforcing intact, and re-pour with additional bottom steel at the bottom of the 12" thick section. Might need to beef up the top steel if you don't meet min steel requirements.

 

[jayrod12]

Depending on your post size, and what fill is under the slab, you might be able to engage enough of a bearing surface below the slab without needing to cut anything out. Worst case you dig out the slab as you mentioned, leaving the existing reinforcing intact, and re-pour with additional bottom steel at the bottom of the 12" thick section. Might need to beef up the top steel if you don't meet min steel requirements.

I'd be shocked if the basement slab had any reinforcing in it. 98% of basement slabs I've seen are unreinforced and vary anywhere from 2" to 10". Residential basement slabs are essentially just poured to cover up the construction garbage in my experience.

 

[Tomfh]

Cut in a footing

 

[EngDM]

I'd be shocked if the basement slab had any reinforcing in it. 98% of basement slabs I've seen are unreinforced and vary anywhere from 2" to 10". Residential basement slabs are essentially just poured to cover up the construction garbage in my experience.

Yea that's my bad, I forgot people do residential. I was just thinking with my commercial cap on.

 

[SWComposites]

Residential basement slabs are essentially just poured to cover up the construction garbage in my experience.

yeah, and hopefully there wasn't organic material in the garbage layer or there may be voids under the slab.

 

[BAretired]

Cutting the slab and excavating for a footing gives you an opportunity to inspect the underlying soil. It is recommended.