Use of earth material Z 1.1

Hello everyone,

the excavated soil material from our site was classified as uncontaminated Z 1.1 with 4 percent foreign materials. I have found out that it may be used for backfilling in construction pits. I was advised against building our slab or a terrace on it. But how about using it as filler around the house?

Is there anything speaking against it?

Let it be, I was so stupid and did it, the end of the story was that the terrace settled, as did the paved path from the entrance to the terrace. I removed all the slabs from the terrace again after 3 years and realigned them. Paving after 6 years. You can never compact soil that has been loosened, no matter how much it is compressed and tamped, so that rain does not compress it again. Please only use mineral concrete. My opinion and experience

But what about using it as filler around the house?

If you can use the soil there, then do it. But stick to it and do not use it as a base for the terrace or similar. For that, please fill and compact it in the usual way with gravel in sufficient depth (because that does not work with your excavation material).

Thank you for your reply. Why do you think my excavation cannot be compacted? 4 percent foreign materials (bricks and concrete) is not much.

Thank you for your answer. Why do you think that my excavation cannot be compacted? 4 percent foreign materials (brick and concrete) is not much.

It is not the 4% that is the problem. The remaining 96% cause you not to be able to compact the excavation properly.

Google "construction of terrace subsoil" or "driveway subsoil." Then you will see what the correct structure is. Not with soil, but with gravel.
It looks like this:

I hope this is not meant to be to scale. For a conventional curb with a height of 25cm, which can still be managed alone by a DIYer (weighing 34kg), the gravel layer of 10-15cm would be far too thin and the crushed stone layer of also 10-15cm would be way, way too thick.

You should also try to make the substructure at least somewhat frost-free. It doesn’t have to be 100cm deep for the extreme winter with 4 weeks at -25°C. But I would gravel down to a depth of 50-60cm.

If you’re smart, you talk to the civil engineer and have the areas where later a terrace, parking spaces, paths, etc. will be placed already gravelled and compacted when the foundation for the slab is made. Because compacting and vibrating larger areas... that takes skill or at least practice.

Soil can’t be compacted properly, and that also applies to crushed stone or gravel.