Drainage in the basement - technically necessary or not?

Good morning,

I have a question for the group! It concerns a soil survey in which two variants are explained for securing the basement against moisture. I have attached the soil survey.

My question now refers to the alternative with the white tank, which was also installed with us. Do I understand correctly from the soil survey that if I build a white tank, the ground filling up to the planned terrain surface level must be carried out either with granular soil (sand, gravel, etc.) or with drainage boards at the basement walls? And what is meant by the concluding words that "a natural discharge for the stagnant water is given"?

For background. I insisted on the installation of drainage (we have a hillside property), although my site manager and the basement builder said that drainage was technically not necessary. The basement was backfilled with a silty-clayey/sandy soil mixture. Drainage boards were not installed on the basement walls. In addition, a coconut-coated drainage without inspection shafts was installed at the corners of the house. An expert criticized that the drainage was not executed according to DIN 4095.
I then had the drainage removed and incurred additional costs of about €15,000 for the disposal of the no longer compactable soil and the new filling sand. The site manager and basement builder now argue that the drainage is not necessary according to the survey. That is only true if correspondingly granular soil or drainage boards are installed exclusively. Or do I misunderstand the passage in the soil survey?

Since neither exclusively granular soil nor drainage boards were installed, this is a planning error by the site management or the basement company. In addition, the drainage was installed incorrectly.
It would be great if you could shed some light on this somewhat tricky situation.

Regards

Morning,

Background: I insisted on installing a drainage system (we have a sloped property), although my site manager and the basement builder said that a drainage system was not technically necessary. The basement was backfilled with a silty-clayey/sandy soil mixture. Drainage boards were not installed on the basement walls. Additionally, a coconut-wrapped drainage without inspection shafts was installed at the corners of the house. An expert criticized that the drainage was not executed according to DIN 4095.
I then had the drainage removed, incurring additional costs of about €15,000 due to the disposal of the soil that could no longer be compacted and the new backfill sand. The site manager and basement builder now argue that the drainage is not necessary according to the expert report. That would only be true if exclusively appropriate loose soil or drainage boards were installed. Or am I misunderstanding the passage in the soil report?

Since neither exclusively loose soil nor drainage boards were used, this is a planning error on the part of the site management or the basement company. Furthermore, the drainage was technically installed incorrectly.

Regards

Hello,
according to the soil report, there are two options:

1. Option:
Sealing according to W 1.2-E (soil moisture) but only with a ring drainage according to DIN 4095. Additionally, the working space must be backfilled with well-draining material. Drainage mats are recommended as additional protection but not mandatory. However, the drainage and gravel are mandatory!

2. Option:
Sealing according to W2.1-E (pressing water) or WU concrete. No additional measures are necessary here.

The white tank (waterproof concrete basement) can permanently stand in groundwater. Therefore, drainage is not necessary as the site manager and basement builder stated. Also, neither permeable material nor drainage mats are required.

Best regards

Oh, I see: The lower paragraph about the stagnant water is important for the structural engineering. It concerns the water pressure acting on the earth-contacting components. This pressure can be reduced by additional measures. However, this pertains to the structural engineering and not the sealing against groundwater.

Therefore, the more relevant question is with what water pressure/earth pressure in the structural engineering the basement wall was calculated.

Hello,
according to the soil survey there are two possibilities:

1. Option:
Sealing according to W 1.2-E (soil moisture) but only with a ring drainage according to DIN 4095. Additionally, the working space must be filled with well-draining material. Drainage mats are recommended as additional protection, but they are not mandatory. However, the drainage and gravel are mandatory!

2. Option:
Sealing according to W2.1-E (pressing water) or waterproof concrete. No additional measures are necessary here.

The white bathtub can permanently stand in groundwater. Therefore, the drainage as written by the construction manager and the basement builder is not necessary. Also, neither permeable material nor drainage mats are necessary.

Regards

Hey thanks for your reply. :D

Now despite everything, the drainage was technically installed incorrectly (according to DIN 4095 no rod goods, the fleece was not completely wrapped around the gravel bed, I had no inspection shafts at the building corners and the yellow coconut pipes were already partially covered with 5 cm of sludge).
Who has to bear the additional costs if the drainage is dismantled? In my opinion, the construction management/basement builder worked inadequately here even if drainage is not absolutely necessary. If I order a service, I can insist on professional work. If everything had been built correctly, no consequential costs would have arisen due to the faulty drainage. Or am I wrong?

That’s true, you have ordered a service and should be able to expect it. As far as I know, in this case the defect must be reported to the contractor and the opportunity for rectification must be given. At this point, I would try to talk to the construction company and seek legal advice.

Be sure to get an expert if you don't have one yet.