A capillary-breaking layer is a layer of e.g. gravel, filter gravel or similar, which is located below the foundation level and prevents the capillary transmission of soil moisture or groundwater.
As an alternative to the gravel layer, other materials are also suitable for protection against moisture by interrupting capillarity.
Before new rules for building waterproofing were laid down in accordance with DIN 18195 (e.g. black and white tubs), capillary-breaking layers were only used to reduce moisture in basements and floors adjacent to soil.
If a foundation is about 1 m deep below the earth's surface, the gravel layer also served as drainage under foundations and floor slabs. This avoids water accumulation below the foundation . These can lead to material damage due to frost and thaw changes.
Such a capillary-breaking layer is formed by a 15 cm thick layer of non-cohesive aggregate (e.g. coarse gravel 16/32). This gravel must be free of dirt and not too fine. Even a layer of dust on the rock can negatively affect capillarity.
type of soil, the highest groundwater level and the use of the building determine the type and effort of the waterproofing measures. According to DIN 18195, an additional waterproofing membrane must be arranged in the event of increased requirements.
Before concreting a cleanliness layer, floor slab or foundation,
aPE film or fleece laid out on the capillary-breaking layer before concreting the floor slab, foundation or cleanliness layer will often help prevent concrete from running into the gravel.
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