Can I Dig a Basement Under an Existing House?

Creating a basement generally is among the first steps in constructing a new home. Building a basement under an existing home often is possible, although certain conditions must be met to ensure that this project is a success. Moving houses and building new basements are intricate tasks that require the expertise of professional, licensed contractors.

The main reason for building a basement under an existing home is to enlarge the living or storage space on the property. The usual means of accomplishing this is to build on an addition to the perimeter of the home or to build upward, adding another story. While these are the ideal ways to increase the size of your home, they not always are possible. Limited yard space, as well as building codes, may limit these more affordable and executable methods of construction in some areas.

When determining the feasibility of digging a basement under your existing home, you must take several factors into consideration, including the cost, insurance and timeline. Contact your local building department to discuss the regulations and restrictions that affect your building project. Talk to your insurance company about the necessity for special requirements during the construction process. Get bids from house-moving companies and excavators. "The average price of building a basement under an existing home is generally at least 50 percent more costly than building a new basement on an empty site," advises John Taylor, a licensed contractor and the owner of Taylor Construction in Lindsborg, Kansas.

The safest and most effective way of providing the necessary space for excavating and building the basement is to remove the home from its foundation and set it off to the side. A house moving company usually does this by reinforcing and bracing your home, then lifting it off the existing foundation or pad with a crane and lowering it onto a cleared area near the original site. Nearby houses, trees and other structures may prohibit setting your house in a different location. If the movers can't relocate your house, they may need to raise it with jacks or a crane and brace it several feet off the ground with blocks and tie-downs.

Excavators usually use backhoes to dig out basements in open sites. If your house is set off to the side, this is a quick and straightforward method of removing the soil from your basement site. If your house is elevated above the digging site, your excavator may dig a single entryway into the basement area, and then use a skid loader to scoop out and remove the soil under your house.