Cementitious Tanking

Internal Systems in Existing Structures

‘Tanking’ is a specific type of waterproofing which functions by blocking water out of a structure, by including a barrier product on or within that structure.  By blocking the pores in the masonry, water is totally blocked out, then the internal basement/cellar environment is protected and remains dry.

The process is referred to as ‘barrier protection’, (or ‘Type A (barrier) protection’ within British Standard 8102) which describes various types of waterproofing systems generally.

If looking at the use of tanking, what do we need to consider?

Effective tanking requires good preparation of the substrate to ensure the tanking can bond thoroughly to the structure. This is achieved by removal of existing plasters, paints and surface coatings.

Tanking is a generic term typically used to describe waterproofing of walls below ground and may be for repairs to walls or a full system including all walls and floors etc which offers greater protection.

Forming a bond with the substrate: In existing properties, tanking is applied to the internal face of the structure, with a variety of products potentially being employed, such as multi-layer cement based products, or chemically modified cement slurries which are applied over a base coat renders (which provides a flat/level surface to accept the slurry).

Tanking is often applied externally in new constructions however will then require additional physical protection prior to back filling to prevent damage occurring to the tanking systems.

Historically, and less commonly nowadays, older basements often had liquid applied bitumen based systems or mastic asphalt. In all cases, the tanking is designed to block out water, however the more modern products such as Kenwood tanking slurry and renders have the benefit of allowing the passage of water vapour which reduces the build up of moisture behind the system.

Because tanking in existing structures is applied to the internal face of the structure, it is particularly reliant on the formation of a bond between the tanking and the surface or substrate on which it is applied. The reason for this is that water under pressure moving through the structure, will bear upon the tanking barrier when it reaches the internal face and hence the requirement for a good bond. One possible way to address this is to properly prepare the surface of the substrate, so that the tanking can ‘key’ to the surface on which it is applied. This means we often utilise scabbling and diamond surfacing to remove surface latiance along with the use of products such as Kenwood rapid which provide excellent adhesion and consolidation of the structure.

The key aspect to remember here, is that the experience of Kenwood Plc ensures that we’re experts in waterproofing such structures and have the knowledge and appreciation of the needs and methods to successful tank basements and vaults.

More modern construction such as reinforced concrete, can often lend itself to the application of internal tanking systems because substrates (if properly prepared) can be extremely strong, and designed to easily accomodate the  imposed loads.