External basement waterproofing

Wet basements can not be fully utilised and can endanger the building structure.  We offer four methods for making basements usable again by applying a new, permanently safe waterproofing: From the outside with polymer-modified thick film sealants, mineral sealing slurries or cold applied self-adhesive waterproofing membrane – whereby the entire external wall area is treated and thus protected from water penetration. Alternatively, the waterproofing can be achieved by installing the external waterproofing from the inside via gel injection. This method can also be used when a new sub-basement is added to a house. In this case, the wall/floor junction is waterproofed externally without having to excavate.

Koster Aquatecnic Ltd advice sheets give pratical information on external basement tanking. Please click on the links to display in a new window:-

Advice sheet 5 : External Basement Tanking with KOSTER Deuxan 2C Thick Film Liquid.

Advice sheet 6 : External Basement Tanking with KOSTER Bikuplan Self-adhesive Waterproof Membrane.

Show references

External basement waterproofing with bitumen based waterproofing systems

The use of bituminous products belongs to the standard solutions for the positive side waterproofing of basements. The systems are applied in a paste-like form and are therefore seamless. They are easy and safe to use and have crack bridging properties. On clean, solid, stable, gypsum free mineral substrates KÖSTER Polysil TG 500 is applied as a primer. This immobilizes salts present in the substrate and the substrate is solidified. When preparing to waterproof on top of old bituminous coatings KÖSTER Bitumen Primer is used. Pipe and cable penetrations are either coated with the respective thick film sealant or fitted with flanges. To protect against water creeping behind the lower waterproofing connections KÖSTER NB 1 Grey mixed with KÖSTER NB 1 Flex is applied under the bituminous system. To prevent stresses in the waterproofing, rounded fillets are installed in the wall/floor junctions.

The actual area waterproofing is achieved using KÖSTER Deuxan 2C Extratight in two layers applied with a toothed trowel. KÖSTER Deuxan Professional can be spray applied. For greater ease of manual application use KÖSTER Bikuthan 1C or 2C Supertight. The addition of KÖSTER Glass Fiber Mesh is recommended in all Thick Film Sealants and all applications. This allows for a control of the coating thickness and safely absorbs movement in the building. Before backfilling the positive side waterproofing is to be protected from mechanical damages and settling with KÖSTER SD Protection and Drainage Sheet.

Always adhere to the specifications in the respective Technical Guidelines. 

External basement waterproofing with mineral based waterproofing systems

1 Primer
KÖSTER Polysil TG 500
2 Waterproofing pipe penetrations
KÖSTER KB-Flex 200 Sealing Paste
3 Preparing wall/floor junctions
KÖSTER NB 1 Flex
KÖSTER NB 1 Grey
4 Installing fillets
KÖSTER Repair Mortar Plus
5 Waterproofing layer
KÖSTER Glass Fibre Mesh
KÖSTER NB 4000
6 Protection of the waterproofing layer
KÖSTER SD Protection and Drainage Sheet 3-250

Mineral Sealing Slurries are especially robust waterproofing systems with extremely good adhesion to mineral surfaces. They are not affected by moist surfaces and become an integral part of the building structure on which they are applied. Mineral Sealing Slurries are paste-like and are applied seamlessly to the building element to be waterproofed. They are easy and safe to apply and can be installed as rigid or crack bridging systems.

On clean, solid, stable, gypsum free mineral substrates KÖSTER Polysil TG 500 is applied as a primer. This immobilizes salts present in the substrate and the substrate is solidified. Pipe and cable penetrations are to be attached to the waterproofing using proper sleeves or flanges. The actual area waterproofing is achieved using KÖSTER NB Elastic Grey or KÖSTER NB Elastic White in two layers. The installation of KÖSTER Flex Fabric is recommended between the KÖSTER NB Elastic layers to achieve an especially visco-plastic waterproofing layer.

In areas especially in danger of water creeping behind the waterproofing such as wall-floor junctions, a substrate preparation with KÖSTER NB 1 Grey mixed with KÖSTER NB 1 Flex is applied. To avoid stresses in the elastic waterproofing, rounded fillets made of KÖSTER Repair Mortar are installed in interior corners.

Before backfilling the waterproofing is protected from mechanical damages and settling with KÖSTER SD Protection and Drainage Sheet.

Always adhere to the specifications in the respective Technical Guidelines.

External basement waterproofing with cold self-adhesive waterproofing membranes

1 Joint sealing
KÖSTER Quellband
2 Primer
KÖSTER Bitumen Primer
KÖSTER KBE Liquid Film
KÖSTER KSK Primer BL
3 Preparing wall/floor junction
KÖSTER NB 1 Flex
KÖSTER NB 1 Grey
4 Installing fillets
KÖSTER Repair Mortar Plus
5 Waterproofing layer
KÖSTER Bikuplan KSK SY 15
6 Protection of the waterproofing layer
KÖSTER SD Protection and Drainage Sheet 3-250
7 Waterproofing membrane ending
KÖSTER KBE Liquid Film

Fast, clean, and easy: Exterior basement waterproofing with KÖSTER KSK cold applied, self adhesive waterproofing membranes. No drying time, instantly watertight, with a tight control on consumption. Apply a primer coat of KÖSTER KBE Liquid Film on clean, solid substrates. In temperatures down to –10° C use water-free KÖSTER KSK Primer SP. Pipe penetrations are sealed using flanges cut to size from KÖSTER KSK Membranes. In areas especially in danger of water creeping behind the waterproofing such as wall-floor junctions, a substrate preparation with KÖSTER NB 1 Grey mixed with KÖSTER NB 1 Flex is applied. To avoid stresses in the elastic waterproofing, rounded fillets made of KÖSTER Repair Mortar are installed in interior corners.

The actual area waterproofing is generally done with KÖSTER KSK SY 15. It is applied crease free to the substrate. The membranes are overlapped 10 cm. Corners and connections are made according to the directions on the packaging and according to the Technical Guidelines. These areas are covered with KÖSTER KBE Liquid Film. On vertical areas the top edge is mechanically fastened and these fasteners are also coated with KÖSTER KBE Liquid Film. In temperatures down to -10° C use KÖSTER KSK AW 15 instead of KÖSTER KSK SY 15. In this case the overlapped edges, corner details and mechanical fasteners are coated with KÖSTER BS 1 Bitumen Paste. Before backfilling the waterproofing is protected from mechanical damages and settling with KÖSTER SD Protection and Drainage Sheet.

Always adhere to the specifications in the respective Technical Guidelines.

External basement waterproofing with curtain injection

Exterior basement waterproofing from inside the building? In the case of renovation it is not always possible to expose the exterior walls through excavation. For example, where the area to be excavated is built upon, traffic concerns impede the excavation, or the economic cost of excavation is deemed too high. In this case you would first think of an internal (negative side) basement waterproofing, but in some cases, such as in historical buildings or buildings with special architectural requirements, this may not be desirable.

In these cases a curtain injection with KÖSTER Injection Gel G4 is possible: The resin is injected through the wall from the inside to the outside. The resin reacts with water and binds it resulting in a waterproof, elastic solid. The injection is carried out with a special two-component pump, KÖSTER Acrylic Gel Pump, and through patented KÖSTER Distributor Lances. The injection material is dispersed on the exterior wall and in a short time reacts to a waterproofing layer.

An alternative method is injecting KÖSTER Injection Gel G4 into the building member itself. This so-called “area injection” is possible in porous or hollow building materials. In this case the KÖSTER Injection Gel G4 also reacts with any water present to form a waterproof, elastic solid.

Always adhere to the specifications in the respective Technical Guidelines.

Waterproofing of pile heads

1 Reprofiling
KÖSTER Repair Mortar
2 Waterproofing of pile heads
KÖSTER NB 1 Grey
3 Waterproofing layer
KÖSTER Deuxan 2C Extratight
4 Embedded Mesh
KÖSTER Glass Fibre Mesh
5 Gliding Layer


Damage in existing buildings is often caused by leaking pile foundations. Water can enter the building through the construction joints or it makes its way along the reinforcement steel. The waterproofing of pile heads has to withstand heavy loads from the whole building and it needs be easily connected to the area waterproofing.

At first all non load bearing materials and separating substances have to be removed from the surface of the pile head. After that, the surface has to be levelled and reprofiled with KÖSTER Repair Mortar. This reprofiling must also includes the installation of a fillet adjacent to the pile head. KÖSTER NB 1 Grey is used to waterproof the pile head.

The waterproofing on top of the blinding layer is made with KÖSTER Deuxan 2C. Embed KÖSTER Glass Fiber Mesh into the fresh first layer. Before pouring the concrete for the floor slab a gliding layer consisting of two layers of customary PE-Foil is applied between the waterproofing and the concrete. Protect the waterproofing layer from mechanical damage when continuing with the application.

Always adhere to the specifications in the respective Technical Guidelines.

Waterproofing under the foundation plate

A complete waterproofing system in new construction includes waterproofing the floor slab. Compared to the application on top of the concrete slab the installation of the waterproofing layer underneath the foundation plate keeps the foundation dry and the concrete provides a better thermal insulation.

First a primer such as KÖSTER Polysil TG 500 is applied to the clean, sound and solid substrate. KÖSTER Polysil TG 500 is a standard primer that locks existing salts into the substrate, hardens the substrate and provides a better bond between the waterproofing and the substrate.

The main area waterproofing made of KÖSTER Deuxan 2C is applied in two layers with KÖSTER Glass Fiber Mesh embedded in the fresh first layer. It is generally recommended to embed the KÖSTER Glass Fiber Mesh between layers as it provides an easy control of the layer thickness and absorbs the forces created by movement in the building.

Before pouring the foundation plate, PE-Foil is installed in two layers to act as a gliding layer between the waterproofing material and the concrete. The waterproofing layer needs to be protected e.g. by a layer of unreinforced concrete. The vertical waterproofing is connected to the side waterproofing layer underneath the foundation plate. A fillet made from KÖSTER Deuxan 2C is to be installed in the connection area.

Always adhere to the specifications in the respective Technical Guidelines.

 

 

 

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