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 (leg length 2 cm) is to be installed in the connection area or KÖSTER WP Mortar (leg length 5 cm).

Always adhere to the specifications in the respective Technical Guidelines.

1 Primer
KÖSTER Polysil TG 500
2 Waterproofing layer
KÖSTER Deuxan 2C
KÖSTER Deuxan 2C (UK)
3 Embedded mesh
KÖSTER Glass Fiber Mesh
4 Gliding Layer
5 Fillet
KÖSTER Repair Mortar Plus
6 Protection of the waterproofing layer
KÖSTER SD Protection and Drainage Sheet 3-400