Anyone know the going rate per linear foot for a poured concrete foundation? My situation is I will be putting on a 16'x26' addition over a full basement. The newly added foundation will be 3 walls, as it will be tieing into the existing structure. The addition will be preferably over a full basement, but willing to go to a crawlspace if there is a significant cost savings. What I fully need is excavating, 20" wide footing, 10" wide by 8'-9' high walls, basement floor, waterproofing and backfilling. Ballpark estimates?