Basement

A basement is a space that is partially or entirely below the ground floor of a building. In North America it is commonly called a basement, while in many parts of Europe and the United Kingdom the term cellar is used. Basements are typically used for storage, mechanical rooms, and sometimes extra living or working space. The extent to which a basement is finished varies widely.

Construction usually involves a below-grade foundation wall, a floor slab, and waterproofing to reduce groundwater intrusion. Basements require proper drainage around the foundation, a sump pump or French drain, and moisture control to prevent dampness and mold. Finishing a basement adds insulation, walls, flooring, and utilities; an unfinished basement provides raw space for storage or future finishing. Climate and soil influence prevalence.

Safety and regulation considerations include adequate means of egress (such as windows or doors) for sleeping areas, adherence to local building codes, and considerations for radon and fire barriers. Proper insulation, ventilation, and HVAC distribution are important to maintain comfortable and safe conditions.

Basements vary in type: walk-out basements provide direct exterior access, daylight basements have exterior exposure through windows for natural light, and crawlspaces are shallow spaces under part of a building. In some regions, basements are less common due to warm climates or flood risk, while in others they are an integral part of house design.

Historically, basements have served as storage and root cellars and evolved into living spaces as construction practices and utilities improved. Today basements can expand usable square footage, support mechanical systems, or provide emergency shelter in certain conditions.