Floor plan of a single-family house 155m², without basement, 3 children's rooms, 1 office

When I think of ecological timber construction, I think of timber studs with wood fiber insulation (also for the roof), according to EH40 + QNG.

So a normal house. Doesn't really have anything to do with "ecological." But managing with 40QNG plus 50 sqm garage within the budget is close to winning the lottery.

Ok, then I used the term a bit carelessly.

I am surprised by your assessment of the price because we have an offer for a very similar floor plan, which is 10m² smaller, for 505k. Especially since it sounds like my 45k additional costs, calculated by the rule of thumb 10m² * 3000€ + 15k for the facade, are way off. (The first offer had no wooden facade on the ground floor)

We will not build 100% turnkey, even though I wrote that above. But the amount of own work will be relatively small, so I did not list it separately. We will probably only lay the floors ourselves.

I will get offers for the floor plan soon. If your assumption is correct, then I will have to make compromises.

For me, as a lover of light, the nicest side of the house is the southwest because of the afternoon/evening sun. The few days a year when it is too hot for that, you can also keep the blinds down. In this floor plan, the side of the house is not utilized at all (I assume the site plan is oriented north). The building boundary is very generous. I would move the garage more to the north on this plot and plan the house entrance on the northwest side. The garage driveway can then also be used as a walkway, so it’s not that much more paving. The northeast seems very quiet. The green strip also provides some distance to the neighbor. I would see a (further) terrace there, at least an access to the garden. In my opinion, the current terrace arrangement in the southeast is quite nonsensical; you have sun from morning until midday.

You have a height difference of 26 m 3 m. That is about 11%. However, you are only allowed to cut or fill 0.5 m. You should take that into account when planning. Simply leveling everything at the front and then raising it at the back will not work there.

Is there a reference elevation for the house?

ecological timber construction

Whether "ecological" and "timber construction" are identical, an inseparable dual concept, or even opposites, this philosophical dispute could fill volumes and take longer than planning and building a house from the first sketch to the last roof tile. As a construction method-neutral building consultant with four decades of residential planning experience, I would like to point out that houses are built from materials and not from ideologies (can be).
Currently, forestry is not sustainable for the simple reason that too many eco-bio-world-saving vegans mistakenly believe that an ecologically valuable house is characterized by the highest possible wood content in the wall structure, exerting a plundering effect regarding prime wood on the wood market – as a result, too much wood is harvested for forests to still be managed sustainably. A worryingly high and continuously growing share of construction timber should actually be called "blood wood" by the consistent do-gooder.

I therefore urgently advise moderation and deideologization. With genuine recycling (not: shredded downcycling), e.g., reused roof tiles, more sensible things can be done than freshly cutting down trees and wanting to use various materials merely because their woke badge says "cement-free." Building walls from boulders mortared with duckweed may look like the solution to the world’s problems depending on what one smoked before, but it is not. Moderately planned, a house from the ecologically unpolitical local builder is not the devil either.

"Schemabaukörper (building mass model proposal with ridge direction suggestion)"
Do I interpret this correctly as can but not must?

If it is stated that way, then I see it the same. The magic word here is "suggestion" – but it would also have been conceivable that the development plan requires such things as a regulation (official planning symbol actually a double-ended arrow symbol, but depending on the plan legend, it could also have been the shown one). I would rather point this out one time too many than have a building permit rejected because of it.

I am surprised by your assessment of the price because we have an offer for a very similar floor plan, which is 10 m² smaller, at 505k. Especially as it sounds like my 45k additional costs calculated by the rule of thumb 10 m² * 3000€ + 15k for the facade are way off. (The first offer had no wooden facade on the ground floor) [...] I will soon get offers for the floor plan. If your assumption is correct, then I will have to make compromises.

Three mistakes in one post: (1) Offers are not comparable just because floor plans are similar. Floor plans alone are not a useful basis for gathering offers. Also read my posts with the keywords dough rest and setting the course. (2) I primarily advise viewing facades as design features and not tying them to necessarily having to specify the construction as well. (3) Compromises are very bad. The final house gains nothing if its planning originally would have worked one or two sizes larger. And simply removing the boarding from a house designed with a wooden facade is also not the real solution.

We will not build 100% turnkey, even though I wrote that above. But the own contribution will be relatively low, so I did not list it separately. Probably we will only lay the floors ourselves.

I assume you mean the floor coverings (cork / tiles)? – regarding own contribution?
Consider: "expansion house plus" is better than "turnkey minus."

You have a 26 m by 3 m height difference. That is about 11%. But you are allowed to cut down or fill only 0.5 m. You should consider this in the planning. Simply leveling everything at the front and then raising at the back won’t work.

Here the 11% basement rule might advise a habitable basement floor. And it underscores the ridge direction proposal. How exactly does the development plan specify "three full floors"?

Somehow you are planning way too high. Or did you mean the max. wall height?