How To Waterproof An Existing Basement

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Basement Waterproofing (Refurbishment)

Refurbishing an existing basement, or undertaking a basement conversion, will often require the installation or the repair of a basement waterproofing system.

Unlike with new build waterproofing, waterproofing an existing basement is likely to be restricted to the using an internal waterproofing system.

Before the waterproofing specification can be confirmed, it is important to assess the existing structure to determine its suitability for waterproofing. The structure should form the first line of defence from a waterproofing perspective. Walls should be in sound condition and the basement slab should be of strong enough condition so as not to degrade behind the waterproofing layer. It is often a good idea to appoint a CSSW surveyor to perform an initial survey – contact us if you need a CSSW surveyor

Steps should be taken to seal any areas of active water ingress. Koster KD System can be used to quickly seal active water leaks. Koster Repair Mortar Plus can be used to fill voids in walls and floors.

There are two general methods for waterproofing existing basements:

By using Type C Cavity Drainage Membranes or by using Internal type A Barrier Systems.

Type C Cavity Drainage Systems are generally considered to be the most reliable form of waterproofing and require less surface preparation in order to be successful. They will require accessible and maintainable drainage, and in most cases a groundwater sump and pump which will need to be maintained on an ongoing basis.

Type A systems such as Koster NB1 Grey work by creating a waterproof coating that fully bonds to the walls and the floor and prevents water ingress. Surface preparation for this type of waterproofing is crucial. Surface contamination, such as paint and slats, must be removed before the waterproofing is applied.

With the correct planning and specification, a damp, wet or even flooded basement can be converted to provide a dry usable living space that will add value to any property.

Check out all the basement waterproofing products in our shop, and contact us if you need our services, waterproofing contractors, or to understand the cost of your basement tanking project.