WATERPROOFING HELP & ADVICE FROM NEWTON
We are frequently asked the difference between ‘tanking’ and ‘waterproofing’ when people are looking to convert a basement or cellar into a dry space. This article clarifies the difference.
Basement Waterproofing is the general term for all forms, or methods of waterproofing that can be used to keep the basement or cellar dry. This includes the installation of a ‘Type C’ Cavity Drain System to manage water seeping into the property and move it safely away to a pump or safe drainage.
Basement Tanking specifically describes the application of a membrane or coating to the inside or the outside of the structure to stop water entering the habitable space of the property – so essentially making the basement watertight. Within the waterproofing industry this is defined as 'Type A' waterproofing.
What Are The Options For Waterproofing or Tanking an Existing Property?
Option 1 – a Cavity Drain System, comprising waterproof membranes, drainage, pumping and control systems to manage water entering the property and safely remove it
Option 2 – a Tanking Membrane, Coating or Slurry to hold back the ground water from entering the building
Option 3 – a combination of the two for maximum protection – which should be considered if the structure is very porous and so at risk of allowing too much water to enter for the Cavity Drain System to deal with. In all cases, the flow of water should be stemmed as much as possible.
A Cavity Drain System comprises waterproof membranes, drainage and/or pumps working together to safely remove water entering the building
A Tanking Membrane or Coating provides a physical barrier to prevent water entering the building
The Safest Approach
At Newton, we always recommend that a Cavity Drain System be included as part of the waterproofing approach for existing structures as it a much less risky than relying on a tanking membrane or coating.
If the tanking is defective – due to poor installation, preparation or impact damage, water will enter the structure and compromise the internal habitable space. Because a Cavity Drain System does not resist the ingressing water, it is much less susceptible to these issues and will remain effective even when the membrane is slightly damaged.
The waterproofing design should take into account the possibility of full height of water around the structure, even where investigations show that the ground water level is lower than this, as changes to water courses, perched water tables and even burst water pipes can quickly result in full ground saturation and a full head of water pressure.
What the British Standard Recommends
The British Standard for Waterproofing, BS 8102:2009, is used by architects and designers to ensure that basement waterproofing is carried out in the safest possible way.
The British Standard recommends 'Type C', or Cavity Drain Membrane Waterproofing be maintainable. The Newton CDM System utilises drainage channels that are placed at the weaknesses within the structure to depressurize and collect water entering the property. This drainage system includes accessible Inspection Ports which allow for the waterproofing system to be accessible and maintainable. ‘Type C’ waterproofing that does not have these drainage channels is not maintainable and so falls foul of the recommendations within BS 8102:2009, and are not allowed by most of the major UK building insurance companies.
Newton Specialist Basement Contractors will always use a maintainable Cavity Drain Waterproofing System and will provide the home owner with a meaningful, underwritten guarantee for the waterproofing.