New Foundation over Old Foundation
New Foundation over Old Foundation
(OP)
I have a project where they want to build a new light industrial building in the same location the old building was located. The old building was damaged by a tornado. They want to leave the old foundation in place, add a minimum of 3 feet of fill, and then build the new foundation. The new building is larger than the old building so some of the new footings will be located over the old foundation and some will not. The new foundation will be monolithic with about a 6" slab and about 24" deep grade beams and footings. It will be the same construction company that built the original building.
What are your thoughts on this? Assuming adequate compaction, I can't think of any problems.
What are your thoughts on this? Assuming adequate compaction, I can't think of any problems.





RE: New Foundation over Old Foundation
RE: New Foundation over Old Foundation
www.SlideRuleEra.net![[idea] idea](https://www.tipmaster.com/images/idea.gif)
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RE: New Foundation over Old Foundation
Mike McCann
MMC Engineering
RE: New Foundation over Old Foundation
Three feet of additional fill could also be problematic. In my neighbor, that can frequently add up to greater than 1 inch of settlement, and sometimes that much calculated differential settlement.
Like SlideRuleEra alluded to, there may not be problems. I would have the contractor show proof that testing was performed and that it is adequate for the new specs. It may be that the new footings could simply be overdug and replaced with an engineered fill, and compacted appropriatley to help minimize the differential settlements. Have a reputable geotechnical engineer from the area do some borings and look over the plans.
Hope this helps.
- EIT Geotechnical Engineer. I am here hoping to help, and learn a little along the way.
RE: New Foundation over Old Foundation
The original foundation is a monolithic slab-footing foundation so it will all be left. The area surrounding the original building is a gravel parking area for the 18 wheeler trailers the company manufactures. The 3 feet of fill is needed to bring the building up to the required flood elevation. The old building is too low.
The surrounding parking area looks good. There are no signs of any rutting due to the trailers. They have some heavy supply trucks in there.
Thanks again for your input.
RE: New Foundation over Old Foundation
good luck.
RE: New Foundation over Old Foundation
RE: New Foundation over Old Foundation
Most importantly, the owner shall be informed that due to his decision on not to remove the old foundation (a potential saving), he could be facing quite a few unpleasant repairs until meaningful settlement has stopped.
RE: New Foundation over Old Foundation
2. Consider leaving slabs/footing units in place, provided slabs cut to smaller sizes (2x2m);
Subexcavate at areas where you have concerns of uniformity of the substructure/subsoil condition;
3. Cut footings from 3' below the the proposed underside of footing or slab, in your case, add 3' of imported fill would be OK;
4. Surcharge the whole footprint area (extended at least 1.2 m outside the footprint) prior to the foundation work.