Drainage of Rainwater from “Wind-Driven Rain Spaces”

Colin Thoms

, Singapore

Wind-driven rain (driving) rain is one of the most important sources of moisture affecting building façades. The horizontal component of flow given to the rain by the winds also means that it is an important consideration for the design of covered or partially enclosed spaces. Many modern buildings are now designed with spaces which, while effectively covered, are subject to wind-driven rain. That is, there is no external façade or rainwater screening system preventing rainwater being driven into the space. Such spaces are typically balconies, lobbies, mechanical rooms, corridors, recreation areas, etc. For the purpose of this presentation, these spaces are referred to as “Wind-Driven Rain Spaces”. Much research has been done on wind-driven rain, with respect to buildings and their façades, but there appears to have been no direct link as to how this rain affects the spaces identified above. Wind effects on buildings clearly vary with building building height, which in turn clearly must impact on the amount of wind-driven rain entering spaces at various locations in a building.

This presentation covers the development of rainwater systems in general, but with an emphasis on the impact of high-rise construction and the need for engineering intervention in the ad-hoc manner in which rainwater is typically managed for wind-driven rain spaces. It may also be surprising to note that there is a complete absence of any building standard or building code in the global scene that provides the various stakeholders such as architects, engineers or hydraulic consultants with viable solutions – but this can be changed.

Accompanying PowerPoint Presentation