storeys

Storeys, in building terminology, are the horizontal levels that make up the usable space of a structure. A storey is typically bounded above by a floor slab and ceiling and below by a floor slab or the ground. The bottom level below ground may be called a basement, which in some jurisdictions is counted as a storey and in others is not.

The term storey is used in British English, while American English uses the spelling story. Naming conventions for levels vary by region: in the United Kingdom, the level at ground level is the ground floor, with the floor above it called the first floor, then second floor, and so on. In the United States, the level at ground level is often called the first floor, with a basement or subterranean levels below it. Some buildings use terms like lower ground floor, mezzanine, or penthouse to designate special levels that do not fit the standard count.

Mezzanines and half-storeys are common variants. A mezzanine is an intermediate floor between two main storeys and may not be counted as a full storey for naming purposes. Conversely, attic or loft spaces may be counted as a storey if they are fully enclosed and meet local height requirements. Height per storey varies with use and climate, but typical floor-to-floor heights range from about 2.4 to 3.0 meters (roughly 8 to 10 feet) for residential space and often higher for commercial spaces to accommodate mechanical systems and generous ceiling space.

Vertical transit and safety considerations, such as stairs, escalators, and elevators, are central to storey design, along with fire safety, access, and egress provisions dictated by building codes and local regulations.