White tub

A white tub is a widespread technique in basement construction for basement waterproofing against water and moisture (approx. 70 %). Similar in design to a bathtub, this construction is impermeable to water. In this process, the outer walls and floor of a room are made from a single pour of waterproof concrete.

With this type of construction, no additional waterproofing layers are necessary and in many cases no drainage is required. In exceptional cases, ceilings can be part of a WU tub, e.g. if the structure is limited to the outside, which should also repel water, e.g. a canopy.

With the WU tub, all walls are both load-bearing and waterproofing at the same time. This design is a reliable alternative, especially in the case of pressurised water and high moisture loads. However, a precise analysis of the building physics, the loads and the room climate is absolutely necessary in order to reliably install the tub.

The walls can be constructed from prefabricated concrete elements or directly on site with special waterproof concrete. It is important to note that a minimum wall thickness should be observed to ensure permanent water impermeability.

The white tub is integrated in many basements that are threatened by water penetration. This happens due to soil moisture, accumulated seepage water, pressing or non-pressing water and, in individual cases, rain showers and floods. When installing a waterproofing tub, architects therefore take into account the “type of attack” or penetration of the water, the stress and use of the structures or rooms, the climate and the nature of the foundation soil.

So-called waterproof concrete according to DIN 206-1 and DIN 1045-2 is used in the production of the white tank, i.e. standardised, water-impermeable concrete for which a separate guideline exists. The white tub is usually installed at floor level for waterproofing. In-situ concrete with system formwork or triple walls with prefabricated elements are used.

White tubs are now preferred to black tubs. In this construction method, the cellars are sealed with a concrete floor slab and individual brick exterior walls. These have been additionally coated with a black bitumen coating from the outside or with welding sheets to protect them from moisture. The bitumen coating gives the black tank its name, while the waterproof concrete is white or light in colour.

For a long time, white tubs were significantly more expensive than the black version, but prices have now converged. In addition, the lifespan of black tubs is only 30 years, while the white form lasts about 60 to 80 years. Many experts such as the Verband Privater Bauherren e.V. therefore recommend the white variant.

The white tank construction is indispensable especially in the planning and construction of basements where water presses on the building elements from below or from the side. The compact, monolithic design absorbs the permanent pressure in the long term. In addition, the groundwater level in Germany and Central Europe is rising steadily because less drinking water is now being discharged than in previous years.

To this end, builders should take into account that an existing drainage system will no longer be connected to the sewer system. The reason: the rainwater that is supposed to be drained from the house penetrates into the seepage water – and this in turn accumulates and puts more pressure on the cellar walls and the floor.