Base building refers to the part of a multi-tenant building that directly serves and affects all tenants. The base building normally includes the building's primary structure; the building envelope (roof and facade) in whole or part; public circulation and fire egress (lobbies, corridors, elevators and public stairs); and primary mechanical and supply systems (electricity, heating and air conditioning, telephone, water supply, drainage, gas, etc.) up to the point of contact with individual occupant spaces (см. http://www.open-building.org/gloss/bas.html).