It is possible to build a basement under an existing home if you lift the house and excavate beneath it. You need to install a new foundation, walls, insulation, and drainage. Homeowners must hire a contractor to build a basement under an existing home, and it costs an average of $125,000.

If your home happens to sit on a crawl space, adding a basement is doable. A construction company can either lift the house and support it with blocks or temporarily move it to an adjacent location. Once out of the way, the contractor can excavate and pour a new concrete foundation and walls.

Whether you’re digging a basement under your existing home or have one planned in your new property design, building a basement is usually legal. In most cases, you will have to get planning permission from your local council, In the year 2017 there was a 183% increase in homeowners submitting planning applications to dig under their own houses.