Penthouse

A Penthouse is typically an apartment on the highest floor of an apartment building. It usually takes up less than half of the entire (flat) roof of the building. Originally the word penthouse meant a small building with a sloped roof. The modern use of the word started in the 1920s in America. In the age of skyscrapers the "house" on the roof was called a penthouse. A penthouse can also be commercial space.
Types of penthouses.
Office buildings have penthouse office suites. Another use for a penthouse is as a restaurant or Café. Their position on a top floor of a building allows for scenic views while dining. The Museum of Modern Art in New York City has a penthouse meeting area. A penthouse can also house a studio, such as a photographic studio.
Building codes.
Under some Building codes a penthouse cannot be more than one-third the size of the floor below it. There is no limit to the number of penthouses a building can have. The only limit is the amount of space they can take up (one-third rule). Also, some building codes do not allow mechanical or electrical equipment to count as a penthouse unless they are enclosed by a roof.