Living in a 1918 house in Saint Paul of the past 9 years, finally got standing water in the basement last year. Gutted the entire basement to the blocks and slab. Noticing that the slab seems to be about 1-2 inches thick and in very shoddy condition. Had a few water proofer’s out for bids (to include the betonite clay guy). But I still think that keeping the water away from the house is the first concern, not with dealing with it when it gets into the house. Would the best COA be excavating the entire perimeter of the house and installing a barrier on the outside (fixing cracks as we find them) or just dealing with an internal drain system? Also I am planning on pulling out the old concrete floor and I would like to excavate about 3 in of sand and put down some hi density foam for insulation prior to re poring the slab. Am I correct in assuming (I know the joke very well) that I should be re-pouring at least a 3 in slab back to the height of and covering the footings?

Any advice would be greatly appreciated

I'd certainly waterproof from the outside before you do anything inside. Gonna be a big job but it needs to be done.

You'll want at least 4" on the slab.....6" would be better.