Failed Tanking - how to avoid it

Save yourself time money and inconvenience by learning form other’s tanking / basement waterproofing mistakes rather than repeating them!

If you look at the picture below, you will see the damage done by water pressure to a road surface (caused by a burst main) imagine trying to get ANY surface bonded 'tanking' material to stop this!

Yet only several meters away one of our basement systems installations maintained a dry basement - because our systems work to remove water pressure rather than fight it. There are countless other failures of tanking systems - installed by others - that we have had to deal with due to burst water mains, drains or acute and sudden rainfall.

Many people have experienced a ‘failed tanking’ or failed ‘ cavity drainage’ job because they have been ill advised or simply went for the cheapest option even though it was not technically the right one for their project.

It is sometimes difficult to understand the factors that lead to Tanking Failure, that is why we have produced several Flash Animations explaining the problems that cause Failed Tanking and the solutions which Basement Systems provide to overcome them. View Failed Tanking Animations.

This is a render on a pavement vault – an arched brick structure under the pavement that used to be the coal cellar. The render is delaminating because the substrate is too weak to hold it in place with the pressure of water pressure behind it.

Internal tanking is normally fine against just dampness if it is applied to a suitably strong substrate. Tanking such as this may be achieved with cement based renders and screed, asphalt or other waterproof coatings bonded to the walls and floor. Tanking or cellar waterproofing using water proof renders such as Vandex, Vandex Sika, Sika is part of the whole package approach to basement conversions.

Whenever ground water levels rise above the basement floor, the hydrostatic pressure will result in water penetrating the wall and floor fabric as far as the bonded tanking system. This water pressure will continue to push against the applied coatings often resulting in cracking and delamination.

Sometimes this pressure causes differential movement between elements of the structure such as the walls and floor - resulting in cracking at the wall floor joint - or across floor and wall spans with resulting flexural movement causing further cracks in the render and screed.

The inevitable result of this movement is a failure of the tanking system with water ingress and the risk of flooding. It doesn't matter how many times the cracks are chased out and sealed – the problem will keep on recurring as the root of the problem – hydrostatic pressure on a weak substrate has not been addressed.