A basement apartment is an apartment located below street level, underneath another structure—usually an apartment building, but possibly a house or a business. Cities in North America are beginning to recognize these units as a vital source of housing in urban areas and legally define them as an accessory dwelling unit or "ADU". Rent in basement apartments is usually much lower than it is in above-ground units, due to a number of deficiencies common to basement apartments. The apartments are usually cramped, and tend to be noisy, both from uninsulated building noises and from traffic on the adjacent street.[1] They are also particularly vulnerable to burglary, especially those with windows at sidewalk level. In some instances, residential use of below-ground space is illegal, but is done anyway in order for the building owner to generate extra income.[1]
Homeowners will typically rent out basement apartments to tenants as a way to earn additional income so as to offset living expenses. Owning a home with a basement apartment can be an investment. Tenants will provide income to the home owner, reducing expenses, and equity will grow as the value of the property increases.[2]