Internal Tanking - Negative side Waterproofing What is Negative Side Waterproofing? A typical case of negative side waterproofing is where water penetrates the walls of a basement and the waterproofing is carried out from the inside. In general, negative side waterproofing is applied to the side of the construction opposite to the side with direct contact to the water. Negative side waterproofing is more difficult than positive side waterproofing because the water penetrates through the construction member (e.g. walls) and tries to push the waterproofing off the surface.   Ideally waterproofing materials are applied to the positive side of a structure (i.e. the side the water is coming in from), however, if this is not accessible, then negative side waterproofing is necessary.

When to use Negative Side Waterproofing Examples of negative side waterproofing include application of  a waterproofing layer to the:- ♦  inside of a basement. ♦  outside of water tanks or silos. ♦  inside of lift pits/ inspection pits. ♦  inside of tunnels. ♦  exposed side of a retaining wall. ♦  underside of a leaking ceiling.

Product properties for successful negative side waterproofing To successfully waterproof a structure from the negative side the products used should have the following properties:-

♦	be mineral based just like the brick or concrete structure - they have to become part of the substrate.
♦	should ideally penetrate a little into the substrate - this way they can't be pushed off by the water pressure.
♦	be breathable so water vapour can penetrate the surface.
♦	be free of sodium so they don't harm steel reinforcement.
♦	should resist high water pressure from the negative side.
♦	should be easy to apply.
♦	should display self sealing properties to avoid leakages from minor cracks.

KÖSTER Mineral Systems KÖSTER Mineral Systems, including NB1 and KD System, fulfil all of the above requirements for successful negative side waterproofing. The exact products to use depend on many factors, including:- ♦  water pressure ♦  condition of substrate ♦  amount of leakage For further information on the KÖSTER products commonly used in negative side waterproofing please click here.

For more details on product selection and application procedure please view, or download, our Advice Sheet 1 - Negative Side Basement Waterproofing - A step by step guide to using KÖSTER Mineral Systems.