ᐅ Offset/Step between frost protection strip and foundation slab

Hello everyone, we need your expert advice. During the construction of our single-family house, it was discovered that the frost protection skirt under the slab foundation, including insulation, was not built flush. Our frost protection skirt has an offset of about 17 cm (7 inches) compared to the slab. This means that all water can flow into the frost protection skirt, and during freezing temperatures, this will eventually cause problems. The planned design — a flush connection between the slab and the frost protection skirt — can no longer be realized because the house is almost completed. After many discussions with building inspectors and the construction company, the builder has now offered to address the issue by installing a bitumen fillet with a dimpled membrane to somewhat align the surfaces. Our expert believes that this might be a solution, but not a permanent one, and that we will likely have to dig up the area from time to time to check if everything is still in good condition.

Do you have any experience with this issue, and is there any other way — apart from demolition and rebuilding — to manage this problem sustainably?

Thank you and best regards