Basements

Basement, in building construction, is a space wholly or partly below ground level. Basements are typically formed by excavating soil and constructing reinforced concrete or masonry walls below the floor slab. In warmer climates, basements are used for storage, mechanical rooms, or additional living space; in cooler climates they are common as a foundation component and for storm shelter. The ceiling height varies and may be finished or unfinished.

Variations include full basements that extend under the entire area, partial basements, and walk-out basements where one or more exterior doors give direct access to the ground level. In some countries the term cellar is used for a similar space, especially when used primarily for storage.

Common design considerations include moisture management, including waterproofing, drainage systems, vapor barriers, and insulation. Egress requirements usually mandate at least one exit to the exterior via stairs or windows for habitable spaces. Finished basements may include living rooms, bedrooms, bathrooms, or home offices, with flooring and ceiling treatments installed as appropriate.

Maintenance concerns include dampness, mold, radon, and freezing temperatures in winter. Construction codes govern structural support, ventilation, egress, and energy efficiency. Basements can improve overall building stability on solid soils but can be costly to excavate and waterproof and are not suitable in areas with high water tables or bedrock close to the surface.