What is Drained Protection in Basements?


The protection method commonly known as 'tanking' is referred to as drained protection in the construction industry. This method involves managing groundwater penetration through the implementation of an internal drainage system. This system typically comprises drainage channels and sump pump systems, which are utilized to collect and remove water. Additionally, vapour barrier drainage membranes may be included to isolate the internal basement environment from damp and wet wall and floor substrates. When all necessary considerations applicable to a given scheme are duly considered, drained protection can provide low-risk solutions.

To simplify, this protection method involves lining the walls and floors with dimpled cavity drainage membranes, similar in appearance to the back of an egg box but smaller. The walls are then dry lined and plastered, and the floors are finished in screeds or floating timber. Beneath this layer, a drainage system is installed which will either drain out at low ground if in a hillside position or be linked to fixed floor drains or a sump station.

Drained Cavity Systems

A Drained Cavity within the basement or sub-structure refers to a pre-formed cavity that is designed to intercept and drain away water ingress in compliance with BS8102: 2009 Type C (Drained) protection. This cavity is relied upon to collect groundwater seepage through the structure and channel it to drains or a sump for removal on a permanent basis. It is imperative to ensure that the external basement structure provides sufficient resistance to water ingress to ensure that the cavity only accepts a controlled amount of water when selecting a suitable water management system.

Cavity Drain is a profiled HDPE sheet cavity former that offers a clear and safe route for water seepage into an existing or new basement while also providing a vapour barrier. This low-risk form of construction can be used for all Grades of basement. Cavity Drain is installed inside the basement structure and onto the structural slab.

The design must incorporate facilities for inspection and draining ground water ingress, which may involve the use of Aqua Channel at the wall/floor junction or casting the structural slab to falls to direct water to pumped collection sumps and/or to gravity-fed drainage systems.