What is Top-Down Construction?
In top-down construction, permanent structures are built from the ground up, beginning with a deep basement excavation. This method is the inverse of the more common bottom-up approach. This method involves constructing the basement levels in layers as the excavation continues. The concrete floors in basements act as lateral bracing for the surrounding walls. Slabs for the ground floor and basement are poured into the excavation holes. Since all subsequent below-grade levels have been completed, the floors can now act as lateral bracing for the perimeter walls.
Diaphragm walls, or “D” walls as they are more commonly known, are a type of perimeter wall that provides a foolproof answer to any problem that may arise during underground building. D walls are ideal for controlling groundwater movement and maintaining stable earth retention.