ᐅ Backfilling the Excavation for the Concrete Slab

Good day,

we have purchased an old house with a basement, which is currently being demolished. On the same plot, a new single-family house without a basement will be built, but it will be positioned differently from the old house. Approximately 3.5 × 9 m (11.5 × 30 ft) of the new house will be constructed on the area where the old house including its basement was located (see attached image).

My question is, since the old house had a full basement measuring 10 × 10 × 2.5 m (33 × 33 × 8 ft), how should this excavation be backfilled after demolition in preparation for the new foundation slab?

Best regards
Sven315

Welcome to the forum,

The same thing was done by @motorradsilke through their general contractor.
In any case, the ground beneath the foundation slab must have the required strength and load-bearing capacity.

The old hole must be filled. For this, appropriate materials need to be purchased.

Now I wonder how much more the new house with a basement would cost if the excavation from the new house were placed directly into the old house's hole.

You would then also have a basement where the washing machine, chest freezer, etc. can be accommodated, or a hobby room can be set up. We could not manage without a basement.

Nida35a schrieb:

Welcome to the forum,

@motorradsilke's general contractor did the same. In any case, the soil beneath the foundation slab must have the required strength and load-bearing capacity.

We only had a partial basement, but it was filled and compacted in layers with a special engineered fill. Even under the part of the old house without a basement, the soil had to be replaced to a depth of about 1 meter (3 feet) because it was just non-load-bearing sand. This engineered fill was used there as well. The general contractor handled all of that. Before pouring the foundation slab, the soil strength was checked again.

However, I would make sure that this engineered fill is only placed where the new house will be located (plus 50 cm (20 inches) around it), if technically feasible. At least in the upper layer, because nothing grows on this fill. It is so compacted that I wouldn’t want to have more of it on the property than necessary.