Are secondary construction costs realistic?

Certainly. How do you already know that you don’t need an entrance platform?
The entrance platform is one of the few things you only know if you need once the house is already built and the yard is being done, you don’t know that beforehand!

Okay.

The current plan from the draftsman does not include a platform, but we are including a hypothetical platform in our financing. I don’t want to be accused of naivety again.

I basically didn’t think we would have an entrance platform until we moved in. Then a landscaper measured the heights and now it unfortunately can’t be avoided because the slope from the front door to the property boundary would be too steep.

Do you know what an entrance platform is? A splash guard? Your draftsman will not draw in some things you need... again: splash guard, entrance platform and rainwater... 10000

Okay. The current plan from the draftsman does not include a platform, but we are including a hypothetical platform in our financing. I don't want to be accused of naivety again.

Did the planner also plan the access? In other words, what is your reference height of the raw floor and at what height is the sidewalk or the street in front of your house?

Okay. The current plan from the draftsman does not include a platform, but we are including a hypothetical platform in our financing. I don't want to be accused of naivety again.

If you are building a timber frame structure, you either need a platform or, with ground-level entry, elaborate grids on the facade. To my knowledge, there must be 15 cm between the ground and the house to avoid damaging the wood and the facade. There is also a DIN standard for this. So definitely plan for something! However, I am not yet very familiar with the topic, so this is just a rough hint.