ᐅ Mistakes When Pouring Concrete for a Prefabricated Basement – Consequences and Experiences?

Hello dear forum,

Our house construction has gotten off to a great start (sarcasm): The construction crew simply forgot to install the formwork for the precast elements at the floor junction, and the concrete flowed out at the bottom. As a result, we could no longer be sure that there are no voids within the wall structure and that the 25/30 waterproof concrete wall is actually fulfilling its purpose and is watertight. For the joint sealing tape, they didn’t use Pentaflex (or a similar product) but instead just pressed a sheet metal strip into the freshly poured floor slab. When we asked about this, we received the following explanation: "These joint strips are purely structural, designed to counteract negative water pressure from the waterproofing. This means water cannot flow from the inside to the outside beneath the walls. This has nothing to do with the primary waterproofing on the exterior."

The basement construction company admitted the construction team’s mistake and therefore executed the basement as a black tank waterproofing system. (However, what we ordered was not a “white tank” system but a basement built according to the soil report specifications with waterproof concrete and sealed joints.)

My question: Is this construction method now worse than what we ordered or possibly even better? (Aside from the fact that, of course, we don’t know how many voids may have formed between the formwork.)

Can anyone estimate whether this changed execution as a black tank might lead to increased follow-up costs, for example, during backfilling of the excavation?

In your opinion, is there any reason why the 5-year warranty might no longer be sufficient?

Thank you very much for your attention

Clarissa