👉 Undercroft, in construction and engineering terms, refers to a portion of an underground structure or a tunnel that is used for ventilation, cooling, and access. It is typically located beneath the surface of the ground and serves as a means of reducing the temperature inside the tunnel or underground space. Undercarths are often used in tunnels where it is necessary to maintain a constant air flow through the building. They can also be used to provide additional protection from external factors such as earthquakes and flooding, and to
