House building and cellar: the black bath

In Germany, most of the houses have a cellar. The basement outer walls as well as the base plate have contact with the soil. This in turn always has a certain degree of humidity, which can vary depending on the region and circumstances. This water content is responsible for the numerous damp basements of many old and existing buildings. The first reasonably effective sealing systems involved extensive sealing with bitumen or tar - hence the name black tub.

Almost everyone connects cellars with moisture

In Germany, the cellar belongs naturally to the houses. A relatively large exception are prefabricated houses, especially older existing buildings. In recent times, prefabricated houses are more often equipped with cellars. The biggest problem for every cellar is moisture. It is present in the soil at different levels.

This is how experts speak of different scenarios.

  • Soil moisture
  • Leachate
  • Groundwater

Soil moisture and leachate

Soil moisture indicates the basic moisture content 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 leachate. Depending on the soil consistency and groundwater level, the seepage water can have accumulating or non-accumulating properties, ie it can not flow out or flows relatively quickly.

Leachate and groundwater

This requires data on regional average rainfall, including rain peaks. Depending on the type of soil and groundwater level, leachate may or may not accumulate or flow differently. The groundwater in turn is defined by its level. In Germany, it is increasingly common to observe that houses are literally in the groundwater.

Pressure and coating water

In this case, speak of pressurized water or pressurized water. From all three values ​​(soil moisture, leachate and groundwater) and the soil composition is then formed explicitly from the rain and melt water (leachate) nor the stratified or adhesive water. Water that does not or very slowly drains off. Depending on the given conditions, this interplay must be taken into account, especially in cellar construction.

Basement construction according to the water-bearing soil properties

The cellar construction techniques are subdivided into different areas.

  • white tub
  • brown tub
  • black tub

The black tub emerged from the cellar seal, which became more and more popular from the middle of the 20th century. So the cellar construction was already as follows.

  • Floor slab (mostly made of concrete)
  • bricked, ascending basement walls

Formation of the black bath

To seal the basement walls against ingress of water, tar was first used. Unprotected exposed to the water but has a low longevity of 20 to 30 years. It was also found that the water also presses from below. For a long time, submersible pumps were the solution.

Although outdated, still today (in new buildings)

So it has gone, and has extended a tar layer on a bottom plate. Thus, the tar seal includes the entire basement like a tub. For new buildings, the black tub should be irrelevant today. However, there are still construction companies that have not familiarized themselves with the white tub or even titled them as a tree fishing rod because of their vapor-permeable attributes.

Great mistrust of the white bath

Also, many construction companies are unaware that modern technology today offers mature products and building materials for efficient white bathtubs. In addition, however, it often comes through the executing companies to serious errors in the construction of white tubs. So it is not surprising that the black tub is still used in new buildings today. Or combination variants from both techniques.

The black bath in old and existing buildings

However, the black bath is still of great importance in the renovation of old buildings and old buildings. A self-renewed and refurbished black tub protects your house for at least 40 years and more.

The construction of modern black tubs also takes into account the short life of bitumen in contact with water or in case of direct backfilling of the outer wall due to mechanical influences. Therefore, the (lateral) renovation of the bricked cellar walls is carried out as follows (from inside to outside).

  • masonry
  • primer
  • bituminous waterproofing, between 3 and 7 mm
  • perimeter insulation
  • bubble membranes, optionally with drainage function for condensation
  • backfilling

However, the renovation of the floor slab in the black tub is a challenge and is correspondingly costly.

Tips & TricksBecause we have addressed the disadvantages of the white tub in this article: only properly built is the white tub better than the black tub. For this, it is absolutely necessary to commission a neutral construction supervisor with the construction site control. The sealing bitumen used today has not much in common with the previously used tar. Modern bitumen waterproofing systems are specially tempered and extremely resistant. Another problem is the ever-increasing groundwater level in many regions. On the one hand, there are fewer groundwater withdrawals, and on the other hand, many building authorities are forbidding drainage of drainage water into the sewer system. Instead, it also becomes leachate, which raises the groundwater level.

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

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