Terrestrial

Basement Waterproofing - New Build

Waterproofing is an essential consideration for anyone who is building a basement which they intend to use for storage or habitable accommodation.Too often basement waterproofing is not given high enough priority and as a result a cheap and inappropriate basement waterproofing option is used to try and get inside an unrealistic budget. This often leads to failure and the resultant consequential losses can be disastrous for the owner of the building or property.

New build basements are often designed and built from well graded and even 'waterproof concrete', concrete block or blocks with concrete infill. A well designed and built structure will generally form the primary resistance to water ingress as the concrete is too dense for water to pass through. However we must always be mindful that where there are construction joints there is risk of failure even if waterbars, hydrophilic/hydrophobic strips are well installed.With this borne in mind it is always a recommendaation that as well as the structure itself, a secondary form of basement waterproofing is adopted even if the structure is new and/or built from 'waterproof concrete'.When the concrete construction itself is considered to be integrally waterproof this is described as type B form of basement waterproofing.

Where the structure is not considered to be integrally waterproofing then we have 2 options for dealing with the potential for water ingress. One is to Tank it and the other is to waterproof it with a Cavity Drain Membrane.Tanking a basement means that a product is applied internally or externally and is designed to physically stop and hold back the water. This is referred to as Type A basement waterproofing.A Cavity Drain Membrane system is applied to the internal face of the earth retaining structure where it can accept the ingress of water depressurise it and manage it to a safe evacuation point. This is referred to as type C form of basement waterproofing.

Tanking as a form of basement waterproofing to new structures has inherent risks. Whether you apply it internally or externally to the structure tanking systems need to be applied 100% defect free to be affective, if water is delivered under pressure against the structure. As dispute and High Court case between two companies Outwing Construction and Thomas Weatherald has set a precedent in the basement waterproofing industry and UK law. The ruling in the High Court of Justice was that it is not reasonable for a tanking or waterproofing system to be applied 100% defect free. What this means is that if you design for or apply a basement waterproofing system to the structure which needs to be 100% free of defects to work and it fails you can be liable for the consequences of that failure. By their very nature all tanking systems need to be 100% defect free to work when tested by water under pressure from the ground.