Temporary storage of excavation from the neighbor's property?

One more concern: If the neighbor goes bankrupt, you may have to remove the excavation at your own expense.

It is very unlikely to go bankrupt already in the shell construction phase - that usually happens later

I'm really glad that I only called the neighbor and was able to put our piles on his property - for anything else you would have been looked at here more than sideways.

Phew, things went differently here as well. My neighbor neither asked me nor knew himself that his sand and materials were placed at my place. His construction company had arranged that directly with my construction company, when our construction begins and where there is still space, etc.

His construction company arranged directly with my construction company when our construction begins and where there is still space, etc.

Which is basically a great approach, as long as the new owners do not get annoyed by fundamental considerations regarding the "external use".

One more concern: If the neighbor goes bankrupt, you may have to remove the excavation at your own expense.

Normally, something like that falls within my area of responsibility when I act as a "Reichsbedenkenträger," but here the depth of the conceivable risks really surprises me.

It can also happen that, due to the glare from the neighbor’s roof tiles, a large pile of earth is accidentally dropped from a high-flying airplane because the evasive action required to avoid the glare necessitates a different course. Unfortunately, neither the source of the glare nor the (foreign) airplane, whose transponder had failed, can be located. In that case, you will also be stuck with the disposal costs for the additional earth.

It's interesting what can be attached to apparent trivialities.