A high-rise is a tall building that has a large number of stories or floors, usually more than six, and that contains an elevator to access upper floors. The building can be used for commercial purposes, where a large corporation accommodates their offices or where a number of different business offices are housed within the same building. The building can also be used for residential purposes that can house apartments or condominiums. There are also some high-rise buildings that accommodate both commercial and residential properties, also known as mixed-use buildings. This takes place when the lower floor(s) are used for business purposes (usually retail businesses) and the upper floor(s) contain apartment or condominium units for residential use. This is an extremely effective building technique in cities where land is scarce. Due to building codes, high-rise buildings are constructed using steel frames to provide stability for the structure.