Floor plan, living on one level, please provide criticism and suggestions.

I understand that it is no fun to carry a laundry basket up 4 floors. Still, it is worth considering whether it is simply easier and better to plan with 2 floors. Building with the slope is always easier than against it. Good if you are not planning for later, when the legs no longer work, then you do not have to take it into account - but you can if you want.

Response from the municipality:

The floor area ratio (floor area ratio) and thus the maximum allowable floor area (footprint) are based on § 19 of the Land Use Ordinance. The development plan for Lilienstraße sets a maximum allowable floor area of 170 m². The decisive area is the one located behind the street boundary line (building boundary) set in the development plan. On two parcels, you will also find delineations of areas for garages. When determining the floor area, garages and parking spaces with their access routes, among other things, must be included.

Regulations for exceeding the maximum allowable floor area can be found on page 6 under section 2.3 of the development plan. According to this, the maximum allowable floor area – in addition to the permitted exceedance of up to 50% according to § 19 paragraph 4 sentence 2 of the Land Use Ordinance – may be exceeded by a further 50%, provided that this additional exceedance exclusively concerns non-fully sealed parking spaces and access routes (e.g., grass grid stones).

Attached is the calculation, what do you think?

This is already (apart from the outdated development plan) the best case to be expected! A relief!

However:
- The building is slightly too large (a waiver might already be needed here; often “rounding down” is not possible. Even 170.15 is 0.15 too much – some building authorities are very strict about this)
- Another 2.5 m² must be saved somewhere (255 m² max, currently 257.5 m²). This should be possible by replacing the driveway with grass grid stones.
- The paved areas listed in post #12 are almost all not possible (exception: the covered area of the terrace). Everywhere else (except the covered terrace area), only grass grid stones or similar can be used.
- To my knowledge, the utility room (HTR) may not be used as a boundary building, so I would not name it as such in the building application. Possibly swap the laundry room and utility room?

Overall remark on the planning:
The planned building is “fighting” against the plot. You can do that – but it will be more expensive (than planning with the plot).

As soon as the garage and the utility room move under the house and are only accessible from the outside, there is no longer any problem with the areas. The ground-level "bungalow with air space" design and mini upper floor could be realized. The feeling of being at ground level is fully preserved, only the cars drive slightly downhill instead of slightly uphill. This descent can be kept minimal through clever terrain modeling, so that nothing needs to be removed. Going up to the main floor is also possible without steps and with only a slight incline. It's just not cheap.

Is there even a link to it?

That was probably too long ago - I presented the first plans here 8 years ago. I can't find it anymore either. To live at ground level on our slope, we ultimately paid easily two and a half times per square meter of living space compared to what it would have cost in a city villa on flat ground. In between, I had to take a deep breath because we had a lower desired budget. Nevertheless, we were able to manage the project.

Is your house on a 500sqm plot?

There's a 14 missing in front of that. But that's not the fundamental problem. A house that can be lived in at ground level is feasible on the plot with the relatively shallow slope – the possibility to cellar a part for cars and technology practically suggests itself. In the Bergisches region where we live, this is also not uncommon.

Now you’re being petty

Even 170.15 is just 0.15 too much – some building authorities are very strict about this)

I was told differently once. Building authorities have some leeway in certain matters. This certainly doesn’t apply to exaggerated “wish-for-anything” demands, nor to limits where a third party is disadvantaged or involved, or could be involved afterwards. “5% over is permissible at discretion before the file has to be reviewed again.”
However, in this case it might indeed be that 170sqm is already seen as very generous. In addition, other larger plots have to manage with the same 170sqm. So whoever pushes this to the limit is not just making “friends” with the building authority.

The paved areas entered in post #12 are almost all impossible (exception: the covered area of the terrace). Everywhere else (except the covered terrace area) only grass pavers or similar can be used.

You’re right about that (sorry, , for the writing style, but I had to visualize this for myself once again)
According to § 19 of the Building Use Ordinance, you are allowed to use 85sqm for ancillary facilities. Ancillary facilities include paths. These must be made of permeable material. The main terrace counts towards the 170sqm. 61sqm plus access path (as far as I know still 5 or 6 meters deep, 4 are not enough) plus access to the front door plus a larger terrace are not possible.
Further maximization should only apply to a necessary parking space. Simply adding up the possibilities is not possible. It is always a limiting additional option in terms of understanding.

HTR may not, to my knowledge, be used as boundary development

There is no boundary development after three meters. However, as I said before: the zigzag game with technology (supply outside of geothermal heat) and HAR into the house is silly and expensive.

I understand that it’s no fun to carry a laundry basket up and down four floors.

Hehe, I wouldn’t be keen on that either. But I wouldn’t want the cramped squeezing in the corridors and no chance to be by myself somehow, so I prefer to spread out over two floors and have an airy staircase instead of those narrow corridors.

The planned building “fights” against the plot.

Yes, absolutely.

Here, an offset gable roof with a third gable towards the street is advantageous for natural lighting inside the house.

I have to add here again: whether an offset gable roof or not – then the air space also makes sense, where from above the (southern) daylight is captured for the living area, which in turn gets its terrace protected to the back. However, 50sqm of air space is no longer nice either, because you get a cathedral-like character that in turn makes the room uncomfortable. Conscious zoning of an air space is as much part of house planning as kitchen planning.

we don’t need 1000m² of lawn, we find that completely overrated,

Your renunciation of playing soccer, walking barefoot, or sunbathing does not count alone: climate protection would be completely underrated in the process. It is not about your enjoyment of the smell of grass or the sight of the color green, but about unsealed ground areas, so that the new development area does not become an incubator.

A 14 is missing in front of that. But that is not the fundamental problem. A single-story house to be lived in on the property with the comparatively shallow slope is indeed feasible

The single-story "bungalow with open space" planning and mini upper floor could be realized.

I think so too.

the possibility of having a basement section for cars and technology is practically given.

I see it that way too. The terrain offers a lot if you give in to the small slope and are open to an airy construction method, even if it is on one more level.

It is probably already too long ago – I presented the first plans here 8 years ago. I can’t find them anymore either.

Oh, what a pity. I can only remember your interior with the central and open staircase.