Installing a basement is a different process than building a basement as part of a foundation. If a house does not include room for a basement, it probably only has room enough for a small crawlspace. Homeowners who want to install a basement will not have enough room, so they will need to lift the house and perform extensive excavations to put in a basement, which can be an expensive process, requiring careful budgeting by homeowners when accounting for costs.
Putting in a basement involves key changes to the foundation, the floors of the house and probably even the slope at which the house rests. Planning for a basement requires detailed analysis and careful plans. Homeowners must hire an architect to make these plans and pay for the necessary local permits required to make such drastic changes. This process can cost several thousand dollars, especially if multiple plans are needed as homeowners scale their budgets.
The house lift itself requires extensive work, including structural posts and framing and a variety of metal or wooden beams. Typical costs in 2011 may be around $12,000, but this varies widely according to the style of house, how large it is and the materials that the structural engineers use. Costs can rise to $18,000 or more.
Excavation refers to actually removing earth from under the foundation to make extra room for a basement. Excavation can be a very expensive process, costing $20,000 for enlarging a partial basement into a fuller size suitable for extra rooms. Excavation is also a variable cost. Many different types of soils have different levels of drainage issues and rock problems. In rocky soil, excavations can be very expensive.
Finishing refers to actually modeling a basement to live in. A basic basement costs only $20 or so per square foot to install once the excavation is complete, but it cannot be used for much except storage. Remodeling to add electrical, walls, floors and making the basement a room or rooms in the house can cost another $20 per square foot when all the costs are added.