ᐅ New Concrete Slab for a New Build – Is Demolition Required?

Hello everyone,

yesterday, the concrete slab for our single-family house was poured by a subcontractor. About two hours after completion, we noticed that at the edges of the formwork, there were settlements and (potential) gravel pockets in the concrete (see pictures).

Probable cause: As shown in the pictures, water and cement leaked out from under the formwork and formed wet cement puddles beside the formwork. We suspect this happened because the PE foil was not laid up to the edge of the formwork (as visible in the photos) and also had gaps or tears in other areas. By the way, the concrete used is waterproof concrete (WU concrete) 25/30.

Now to our question: Is this concrete slab still usable/repairable, or should we insist on a removal and replacement? Our concern is that the slab may not be fully waterproof (due to improper consistency: gravel pockets) and that the house walls on the slab edges will not find stable support.

We would really appreciate your opinion and feedback!

What does your building inspector or expert supervising your construction say? If you don’t have an expert, arrange for one to guide you through the process.

Looks like a minor issue. It can be reworked.

Your certified expert will advise you on everything else.

Marcel_89 schrieb:

For our single-family home, the foundation slab was poured yesterday by a third-party company.

Who in their right mind saves money by having such a job done by a third-party company (which in this case seems more like a general maintenance service than a specialized contractor)? A foundation slab should be part of the scope of work included in the main construction contract with the general contractor or home builder. Gravel pockets usually occur due to an inadequate concrete mix rather than water seeping out from the cement slurry. And as for the claim that the slab could have been "waterproof" ("WU" standard), even the Easter Bunny would only believe that before a hangover breakfast.

Marcel_89 schrieb:

Now to our question: Is this foundation slab usable or repairable as it is, or should we insist on its removal and replacement?

And now a counter question: where do you assume such a low-tier company would be financially strong enough to survive a warranty claim at all?

You should urgently hire an independent construction expert to accompany the build, and ideally also consult a lawyer to review your construction contract carefully (just in case you chose your general contractor or home builder just as poorly).

---

https://www.instagram.com/11antgmxde/
https://www.linkedin.com/company/bauen-jetzt/