A diaphragm wall is a structural concrete wall constructed in a deep trench excavation, either cast in situ or using precast concrete components. Diaphragms walls are often used on congested sites, close to existing structures, where there is restricted headroom, or where the excavation is of a depth that would otherwise require the removal of much greater volumes of soil to provide stable battered slopes. Diaphragm walls are suitable for most subsoils and their installation generates only a small amount of vibration and noise, which increases their suitability for works carried out close to existing structures. In addition, floor slab connections and recessed formwork can be incorporated into the walls.