What is “Tanking”?
The term “tanking” was commonplace during the 80s, 90s, and ’00s, and the terminology has stuck. In simplistic terms,’ tanking’ is a word used to describe the ‘waterproofing’ of belowground areas.
As per its name, these waterproofing systems are applied internally to a belowground structure to keep water and moisture out of the area, very much like a swimming pool, or ‘water tank’ keeping water in.
Many architects and surveyors still, when in conversation regarding below-ground areas, suggest that the section of the house may need ‘tanking’. Realistically, what they may need is ‘damp proofing’, or if live water is present, they will need to be subject to a ‘water management system’.
Traditional Tanking Processes
Traditional ‘tanking’ involved the preparation of the section of the building or substrate, including paint removal and the raking out of mortar joints. Then there was an application of the cementitious layers (up to 5) on top of each other to form a barrier both vertically and horizontally, generally in the form of, slurrys or water-resistant renders (in more modern times, some epoxy resins are used to achieve the same goal).
These traditional ‘tanking’ systems were high-risk, especially where live water was present. There are several reasons this approach was prone to failure, including poor workmanship as a result of poor preparation; failure of the system due to shrinkage, which can crack the introduction of punctured fittings leading to stress cracks and water ingress. They were also very prone to condensation build-up due to their dense construct.
It is also not unheard of for building movement to crack the systems again, leading to issues.
A modern approach to tanking
The traditional systems were very labour-intensive, disruptive, dirty to prepare and introduce and high-risk due to the abovementioned issues.
The more modern system for belowground areas (especially in traditional older buildings with basements or cellars in situ) is known as a water management system or an air gap dampproofing system.
The approach is called a Type-C cavity drained system, which can be connected to drainage and sump pump stations to move live water or can be introduced with natural gravity drainage.
These more modern systems are, without a doubt, the way forward. They are less labour-intensive, less disruptive, more technician friendly to install, use fewer chemicals and are easy to repair damaged. They can also be insulated and dry-lined and are much less prone to failure.
Enlist a PCA expert.
Many non-specialist builders will refer to the ‘tanking’ of belowground areas. Customers, you should be cautious of this terminology as it demonstrates undoubtedly a lack of specialist knowledge and the complexities of creating a below-ground dry space.
You can download a leaflet from our trade governing body, the PCA (Property Care Association), which sets out for you the different types of systems. It gives more information about the British standards bs8102 (2009), the code of practice for the protection of below-ground structures against water from the ground.
We would always recommend that if you require good, sound, experienced advice on belowground structures, you contact a member of the Property Care Association. It is essential to discuss with a surveyor who holds the CSSW qualification (certified surveyor and structural waterproofing) and who can demonstrate their knowledge, experience and expertise to design and install a system that will be fit for purpose.
Our surveyor and company owner holds the CSSW qualification and would be happy to discuss any projects you may have or answer any questions.