Building a sealed basement against pressing water

I have a few questions about the topic of basements. We want to build next year. An appraisal has shown that we have to expect hydrostatic pressure on our property in Schleswig-Holstein. In addition, the water is highly aggressive to concrete. However, we do not want to do without a basement. Now, you keep reading horror stories on the internet from people who have built and whose basements are still damp and cold, with mold and rot. Of course, we do not want that. We also want to use our basement for living. What do you think is the best solution? We are quite unsettled because you keep reading bad things about solutions like the [Weiße Wanne]. Who can advise?

WU-Keller

This is going to be really expensive.
Apart from that, your warranty period is max. 5 years. And then? But maybe there is someone who offers more. Then that person should still be there in case of damage.

I have a few questions about the topic of basements. We want to build next year. An expert report has revealed that we have to expect pressing water on our property in Schleswig-Holstein. In addition, the water is highly aggressive to concrete. However, we do not want to do without a basement. Now you keep reading horror stories on the internet from people who have built and whose basements are still damp and cold, where there is mold and rot. Of course, we don't want that. We want to use our basement for living as well. What do you think is the best solution? We are quite insecure because you often read bad things about solutions like the White Tank. Who knows?

WU-Keller

Hello Baufixx,

how expensive do you think this could get? Do you have any experience with it? And apart from the price, what is the best solution?

That’s going to be really expensive.

Hello,

...Besides, the water is highly aggressive to concrete...

Just so you know: I haven't read/heard such nonsense in a long time. Water always finds its way – regardless of what obstacles might be in its path. The "colleague" house seller seems very "creative" if this statement is based on his assertions.

...We would like to use our basement for living as well. What do you think is the best solution?

Aside from the fact that such a basement certainly brings an additional cost of around TEUR +/- 10 (depending on the house size)...

...We are quite insecure because you often hear bad things about solutions like the white tub.
Who knows advice?

...a "white tub" is the result of soil conditions; if done correctly – maybe not by the self-builder – there is nothing bad about it.

Kind regards

Hello,

I find this polemic not very helpful

This is by no means polemic, rather gallows humor

The fact is that we have a test report on the groundwater, an "assessment of the degree of attack against concrete according to DIN 4030 Part 1". And the result is simply that the water is strongly aggressive to concrete. Hence our concerns about WU concrete.

This standard sets criteria for the assessment of the aggressiveness of waters, predominantly of natural composition of soils and gases containing substances aggressive to concrete on hardened concrete according to DIN 1045. It does not apply to concentrated solutions, such as certain industrial wastewaters.

"aggressive water" is water with components that lead to intensified chemical reactions. Free excess carbonic acid can, for example, cause lime-aggressive water, which is particularly important in the process of karst formation as well as in technical fields. The degree of aggressiveness of the water is a measure of the respective dissolving capacity of the water. Even distilled water, for example, can dissolve minerals from solids.

Building waterproofing: watertight / water-impermeable

The necessary waterproofing measures result from the waterproofness of the existing soil or individual soil layers as well as from the height of the groundwater level. This information can be obtained through corresponding soil investigations (soil reports). It should be noted that for the groundwater level, the long-term (over several years) highest groundwater level is determined. For a first assessment, some responsible authorities also provide information about the groundwater level.

Regarding the stress, a distinction is made between:

Soil moisture and non-stagnant percolation water with sufficiently permeable soil as well as the highest groundwater level below the foundation level, stagnant percolation water in soils with lower water permeability (cohesive soils) and without drainage, if the highest groundwater level lies at least 300 mm below the foundation level (i.e., if soil type and terrain form only suggest stagnant water) and with a foundation depth up to 3 m,

or

pressing water in buildings whose foundation level lies below the highest groundwater level or in the layer water, regardless of foundation depth, immersion depth, and soil type.

Usually, one of the following two waterproofing variants is used:

1. Water-impermeable concrete (WU concrete or white tank):

Using a special concrete mix and reinforcement as well as compliance with certain boundary conditions, a watertight tank of reinforced concrete is constructed. Water-impermeable, however, does not mean "watertight." While a watertight material neither allows water penetration nor passage, in a water-impermeable material water transport through the material is so strongly reduced that the water that passes through can evaporate on the air side. This circumstance should be noted when planning higher-quality use of basement rooms (living spaces (if permitted by building regulations), hobby rooms, etc.) since without additional compensatory measures in water-impermeable components, an increase in indoor humidity can occur. Furthermore, no vapor-tight coverings (e.g., PVC coverings or tiles) may be applied directly to WU concrete structures.

2. Watertight building materials (black tank):

In this variant, the basement components are waterproofed according to the stress described above using coating systems or sheet waterproofing.

Both variants therefore have advantages and disadvantages, for example regarding costs, reworkability of defects, consequences for finishing and use of the basement, construction process, etc. The decision whether the building should have a basement and, if so, which type of waterproofing should be chosen, should therefore be made in close consultation with the architect or an appropriate specialist planner. This point should also receive special attention when purchasing a property.

Although the production costs for waterproofing represent only a small proportion compared to the total costs of building construction, waterproofing is of considerable economic importance because if it does not function properly, high consequential costs arise from damage and especially for repairs, as waterproofing becomes difficult or impossible to access after the building is completed.

From your report, it then follows how your preferred construction partner should execute the basement; moreover, the geologist would surely be able to alleviate your concerns regarding WU concrete if you were to ask him.

Kind regards

alternative

Hello Claudia,
there is now an alternative. In the spring, I came across the ABG Kellerdichtsystem at a trade fair and talked to our architect about it. It was new to him as well. However, he thinks it is quite a sensible solution for us – we also have penetrating water. It comes from gas station construction. Simply put, where no water goes out at the gas station, no water comes into the house.
MartinW