Basement sealing, waterproof concrete white tank

Hello everyone,

I would like to get your expert opinion on the topic of basement waterproofing. We have two offers from different construction companies and I would like to hear your assessment of which basement waterproofing method against pressing water is the better option:


----------------------------------------------
1. Provider
Formwork of the basement, poured on site with 24 CM WU concrete, with 10 cm XPS insulation on top. According to the construction description, execution as "Weisse Wanne":

As a foundation, a floor slab at least 25 cm thick made of watertight reinforced concrete is constructed. Under the floor slab, a concrete leveling layer (d=5cm) with a sliding layer of 2 layers of PE foil above is carried out. The basement exterior walls are also formed and concreted on site with watertight reinforced concrete in a thickness of approx. 24 cm (not exposed concrete). The design is based on structural requirements assuming a soil pressure of at least 200 KN/m2, as well as soil moisture and occasional rising seepage water. The special bond of concrete and steel reinforcement achieves high crack resistance, which is of great importance for the high durability and long-term use of the basement. By constructing the basement as a "White Tub," no drainage is required. Additional costs, as usually necessary, for a soak pit including a submersible pump... are omitted... The basement walls are provided with a 10 cm thick, moisture-resistant XPS insulation on the outside, from the top edge of the floor slab up to the connection to the base plate thermal shell.

Regarding the basement floor it further states: All basement rooms receive a moisture barrier according to DIN 18195.
----------------------------------------------
2. Provider
Supply of sandwich elements, poured on site with WU concrete, thickness 30 cm
Unfortunately, I have no more detailed information here, since the construction description is outdated and I do not yet have a new one containing the exact basement construction. According to the advisor, who is also a master bricklayer, his construction would be just as secure as that of the other builder.
----------------------------------------------

What do you think about this?

Hello,

I would like to have your expert opinion on the topic of basement waterproofing. We have two offers from different construction companies and I would like to hear your assessment of which basement waterproofing against pressurized water is the better option: ...
What do you think about it?

It is not relevant what the participants of this forum think here - the only thing that matters are the written findings of the soil surveyor!

Normally, most construction companies consider the load case "soil moisture according to DIN 18195 T4". So it depends on which "moisture or waters" the soil survey specifies. From this, the design of the basement as a white or also brown/black tank necessarily results.

What you must absolutely keep in mind is that - as soon as the results of the soil surveyor are available - the respective DIN standard is named in the addenda to the contract under which the basement is then designed as the required tank. This way you can exclude that the basement builder refers to perhaps cheaper alternatives. Of course, the execution of the basement must be accepted before backfilling and compacting the soil; preferably by a neutral, external party – meaning, it is always good to commission external expertise to accompany the construction client.

Kind regards

Thank you Bauexperte for your opinion. Unfortunately, I do not have a soil survey for my property yet, but we will definitely do one. Unfortunately, due to an "Aktion" by the construction company, which is really fair, I have to finalize the contract by the first week of November at the latest, and I won’t get a report by then. I will definitely ask the construction company again whether they seal with T4 or T6. With T6, I would be on the safe side.

I was planning to have a building inspector for the basement acceptance anyway. Do you know how much something like that costs?

Hello,

Unfortunately, I don't have a soil report for my property yet, but we will definitely do one.

If you are already the owner of the property, you could bring forward the soil report and get a credit – provided this is also included in the provider’s scope of services – from the provider? I would never recommend building without a report!

I was planning to have a building inspector for the cellar acceptance anyway. Do you know how much something like that costs?

That depends on whether you have arranged just one inspection or several. Try feeding Aunt Google with "Bundesverband deutscher Bausachverständiger" or also "Bundesverband öffentlich bestellter und vereidigter sowie qualifizierter Sachverständiger e.V." With both, you can have experts in your region displayed and have an initial consultation regarding costs with them; to my knowledge, this also works through the Dena (German Energy Agency).
Kind regards

The property has not been purchased yet but is reserved and I have been assured that I can also commission an appraisal there. Thanks for your tips, I will negotiate that with the house builder.

Best regards