Site planning on a gentle slope with filling

May I assume that the planning for the building application was done by the company executing the construction.

14,000€ for gravel. Or 14% of the basement. Installation still to come and for that you will definitely need bigger equipment ;)

I just calculated with us and we also have 5.5% diagonal over the entire property. You can build there without a basement, even though back then we assumed significantly less slope (survey only came after we already had the contract and financing...). But that's not exactly trivial. For a real hillside house that’s a bit too little again. The sweet spot for the slope would probably be a daylight room in the basement, e.g. an office or hobby room, which can then be realized without a light well

Yep, that won’t work with a mini excavator (or very slowly) :D
We actually only had the result of the survey when our house was already fully planned, the first sample selection was completed, and ready for the building application. How it looks with a basement we saw at the neighbors, the outside access to it is below the natural ground level.. the whole house would have to be placed a little higher so that it’s level with the ground floor, which makes it too high.

May I guess that the planning for the building application was done by the company executing the construction.

The building application planning was done by the architect of the general contractor. Why do you ask?

Very few GCs plan with split-level or basement living areas.
Slab, cellar (which is not needed) pushed underneath or retaining wall 1m space slab house these are the standard variants. I came across 3 GCs 6 years ago who deviated from this.

If you ignore the garden issue and only look at the house from the street and it is barrier-free, it fits correctly. As I already wrote, I would even out the height relatively close to the house and then the worst is evened out. The only disadvantage is, if small children are present, their play area is out of sight. However, that grows over very quickly.

And watch what you fill it up with. Trees and co prefer soil

And the 20 euros per ton including the trip I consider almost too little. You better inquire.

Very few general contractors plan with split levels or a basement living area. Slab foundation, basement (which is not needed) pushed underneath, or retaining wall 1m space slab-on-grade house – those are the standard variants. Six years ago, I came across 3 general contractors who deviated from that.

If you ignore the garden issue and only look at the house from the street and barrier-free perspective, it fits well. As already mentioned, I would balance the height relatively close to the house, and then the worst is evened out. The only disadvantage is that when there are small children, their play area is out of sight. However, that grows together very quickly.

And watch what you fill up with. Trees and company prefer soil.

The general contractor didn’t plan much more on this; the floor plan was largely dictated by us, and we fiddled with it for quite a while. The architect then improved detailed solutions... so the general contractor is innocent that not “more” was made out of it :D The children’s play area will only partly be on the property anyway. On the other side of the street is a large playground. So we save ourselves one or another slide/climbing wall on the property :)

For the terrain progression, we have now agreed on a relatively high slope (1.7m) behind the house, which will later be beautified with natural stones and planting or stepped with small walls. But you can decide that much better when you have it in front of you. So, for now (except for lava and installation), it is an inexpensive solution where no huge earthworks will be needed later.

The subsoil will be lava; for the lowered level behind the house, a layer of soil/topsoil will then be applied directly over the excavation for planting. I read that 25 cm should be enough for most plants.

Just for the material it could work if you don’t have to drive too far. In September I paid €15 net per ton of gravel. It was a three-axle truck, with the tractor-trailer it’s about one euro cheaper. But as I said, you also have to put it in place, and a mini excavator and the vibrating plate from the hardware store are several orders of magnitude too small for that.

Make two small steps out of the 1.7m slope and plan them properly. 1.7m properly battered also quickly uses up 3m of space. 1m is also the height from which retaining walls no longer forgive big mistakes.

The subsoil will be lava, for the lowered level behind the house a layer of soil/excavation will then be laid on top directly for planting, had read 25cm should be enough for most plants

25cm of topsoil over subsoil is enough. 25cm over gravel is not enough for most plants, as the water drains downwards. Especially not for trees.