House building and cellar: the black tub

Most of the houses in Germany have a basement. The outer cellar walls and the floor slab are in contact with the ground. This in turn always has a certain degree of humidity, which can vary depending on the region and conditions. This water content is responsible for the numerous damp cellars in many old and existing buildings. The first reasonably effective sealing systems included extensive sealing with bitumen or tar - hence the name black tub.

Almost everyone associates a cellar with moisture

In Germany, the cellar is a natural part of the house. A relatively large exception are prefabricated houses, especially older existing buildings. Recently, even prefabricated houses have been equipped with cellars more often. The biggest problem for any basement is moisture. It is present at different levels in the ground.

  • Read also - basement walls
  • Also read - Build a basement when building a house
  • Also read - drainage basement

Experts speak of different scenarios.

  • Soil moisture
  • Seepage water
  • Groundwater

Soil moisture and seepage water

The soil moisture indicates the basic moisture level of the surrounding soil, because the soil acts like a sponge and also stores water in certain quantities. When it rains or snow melts, this water seeps in as seepage water. Depending on the consistency of the soil and the groundwater level, the seepage water can have damming or non-damming properties, i.e. not or. to flow off relatively quickly.

Leachate and groundwater

This requires data on regional average rainfall, which also includes rain peaks. Depending on the type of soil and the groundwater level, seepage water may or may not accumulate. flows off differently. The groundwater, in turn, is defined by its level. In Germany it is becoming more and more common to observe that houses are literally standing in the groundwater.

Pressure and layer water

In this case one speaks of pressurized water or pressing water. From all three values (soil moisture, seepage water and groundwater) and the soil composition, the stratified or retained water is then explicitly formed from the rainwater and meltwater (seepage water). Water that does not drain or drains off very slowly. Depending on the given conditions, this interaction must be taken into account, especially when building a basement.

Basement construction methods according to the water-bearing soil properties

For this purpose, the cellar construction techniques are divided into different areas.

  • white tub
  • brown tub
  • black tub

The black tub is from the middle of the 20th. The basement waterproofing that came into consciousness emerged in the 19th century. Even then, the cellar construction was as follows.

  • Floor slab (mostly made of concrete)
  • masonry, ascending cellar walls

Creation of the black tub

Initially, tar was used to seal the cellar walls against the ingress of water. However, exposed to water unprotected, it has a short lifespan of 20 to 30 years. It was also found that the water is also pushing from below. For a long time, submersible pumps (€ 33.99 at Amazon *) were the solution.

Although outdated in itself, still relevant today (for new buildings)

So you went and spread the tar layer on the floor slab. Thus, the tar seal covers the entire cellar like a tub. For new buildings, the black tub should be of no importance today. However, there are still construction companies who have not familiarized themselves with the white bathtub or who have not. Because of their vapor-permeable attributes, they even refer to them as a lack of construction.

Great distrust of the white tub

Many construction companies are also not aware that modern technology today offers sophisticated products and building materials for efficient white bathtubs. In addition, the companies carrying out the work often lead to serious errors in the construction of white tanks. So it is not surprising that the black tub is still used today in new buildings. Or combinations of both techniques.

The black tub in old and existing buildings

In the renovation of existing and old buildings, the black tub is still of great importance today. A black tub that has been modernized and refurbished yourself will protect your house for at least 40 years and more.

The construction of modern black tubs also takes into account the short life of bitumen when it comes into contact with water or when the outer wall is directly filled by mechanical influences. Therefore, the (lateral) renovation of the brick basement walls is carried out as follows (from the inside to the outside).

  • Masonry
  • primer
  • Bitumen waterproofing, between 3 and 7 mm
  • Perimeter insulation
  • Knob sealing sheets, if necessary with drainage function for condensation water
  • Backfilling

However, the renovation of the floor slab of the black tank is a challenge and is correspondingly expensive.

Tips & Tricks As we have addressed the disadvantages of the white bathtub in this article: the white bathtub is only better than the black bathtub if it is built correctly. To do this, it is absolutely necessary to commission a neutral site supervisor to monitor the construction site.The sealing bitumen used today no longer has much in common with the tar used in the past. Modern bitumen seals are specially coated and extremely resistant.Another problem is the increasing groundwater level in many regions today. On the one hand, there is less groundwater abstraction, on the other hand, many building authorities prohibit the discharge of drainage water into the sewer system. Instead, it also becomes seepage water, which causes the groundwater level to rise.

Of course, in the construction journal you will also find detailed articles, for example on the white bathtub, but also detailed instructions on how to make a horizontal basement seal yourself.