Is staircase DIN 18065 mandatory or not?

Addendum: The exact same wording is in the Lower Saxony Building Code.

Our house is 6.7m high and therefore falls into building class 1.

Then you can probably do it.
For me, it would be an absolute no-go and would also reduce the house value for a potential resale. But hey - it’s your money and your house.

I suppose the building authority does not check whether DIN18065 is complied with. It is more about the legal situation.

As long as you only use it for yourself, it is unlikely to bother anyone. But if a child falls down, that's a different matter. The architect pointed you to the standard. He is then released from liability.

Every space-saving staircase is steeper and also works. It is not comfortable.

We have the same suspicion. I think we will have to discuss it with the architect again. Possibly a quarter-turn staircase is a reasonable alternative.

We are quite aware of the steep stairs. At the moment, we are renting an old holiday home (Nurdach) with a really small space-saving staircase.

„At the moment“ is a good point. It’s possible that you are currently fit. Just try being sick in bed for two weeks and then your thigh muscles will have to be trained again. That doesn’t happen overnight. If you have to go down these stairs every day, it also takes a toll on your knees in the long run.

Every space-saving staircase is steeper and it also works.

It also makes a difference which rooms are connected. If it’s only the sleeping area, then you might only have to use the stairs once a day. If you really want to live and dwell there, constantly being active and using the stairs with cleaning supplies, laundry, or other everyday items, then I would definitely advise against it.

We are fully aware of the steep staircase. At the moment we are renting an old holiday home (Nurdach) with a really small space-saving staircase.

You know the shortcomings and want to have them again, even bought a plot of land just to economically contaminate it with a hard-to-sell house? – well, I guess it is one of the "blessings"? of a free country that the use of reason is not mandatory. The unreasonable staircase is "set" and the opportunity to discuss the planning is not to be used, desired?

You know the inadequacy and want it back, you even bought a plot of land to economically contaminate it with a hard-to-sell house? - well, it probably belongs to the "blessings"? of a free country, that the application of reason is not mandatory. The unreasonable staircase is "set" and the chance to discuss the planning not to be used desired?

We just want to save 30-40cm so we don't have to redesign everything again. According to the staircase calculator, with a length of 260cm we would comply with all limits... except for the tread depth. This would be 3cm too short.

We will take the advice (almost an accusation) to heart and look at some staircases on site.

We only want to save 30-40cm so that we don't have to redesign everything again.

and not wanting to take the opportunity to discuss the planning?

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We will take the advice (almost an accusation) to heart and look at some staircases on site.

It is easier for a camel to go through the eye of a needle than to find a functioning too-short staircase, as you yourselves say:

According to the staircase calculator, we would comply with all limits at a length of 260cm... except for the tread depth. This would be 3cm too short.

To fit except that it would be too tight is a contradiction. Even ballet dancers do not constantly walk on their tiptoes. Descending stairs backwards may look funny as a gag once in a while, but that wears off. I am still in my mid-fifties, but I would not even wish a minimum standard staircase on my worst enemies... in the worst case, I would be somewhat embarrassed.