what does it cost to put a basement under an existing house
1 Adding a basement to an existing house can cost $30,000-$70,000 or more, depending on the size of the existing crawlspace or half-basement or if the house is on a slab foundation, and how much of the work is do-it-yourself and how much is done by contractors. For a remodeling project that includes adding a basement (either under the existing home or as part of an addition being built), the National Association of the Remodeling Industry offers tips for choosing a contractor, as well as a searchable database of its members.