What is the open space between the ceiling of the top floor and the underside of the roof called?

The open space between the ceiling of the top floor and the underside of the roof is known as a cockloft. This area can be significant in terms of fire behavior and the potential for fire spread. In buildings, especially those constructed with wood frames, the cockloft can serve as a concealed space that traps heat, smoke, and gases, which presents challenges for firefighting operations. Understanding the layout of cocklofts is crucial since they can impact ventilation strategies and pose hazards such as the possibility of fire extending into that space from the floor below.

The other terms mentioned refer to different architectural features: a roof chase typically describes a vertical space used for running pipes or ducts, eaves are the edges of the roof that project beyond the walls, and a mansard refers to a style of roof with two slopes on each side that meet at a flat section at the top. Each of these terms serves a specific purpose in construction, but the correct terminology for the space above the ceiling relates directly to the cockloft.