Is the neighbor building legally and how do I find out?

At the building authority, I was shown a file containing construction plans: A3 (?) illustrations of the exterior facade and the layout inside on the ground floor and upper floor. Also, a top view of the property was included, showing the houses, a garage, and a garden shed. Terraces were not drawn in. According to the building authority, as an adjacent neighbor, I have a right to inspection, which the neighbor should/must have granted me on site in a straightforward manner. So, there should be a view with terraces drawn in? If yes, what is this view called?

These views are called "ground floor plan" and "site plan." If terrace doors are drawn without a terrace, the philosophers can "decide" whether the building authority was deceived or negligent. Theoretically, you could make a request to the building authority to monitor the setback distance of the terrace. But practically, you can be sure that if nonsense is spoken during coffee, you will still hear it well even at 2 meters farther distance. Enforcing your "right" will therefore bring you nothing but a poisoned atmosphere.

However, if you want to banish your neighbor as far as possible, I can reveal to you the simple trick my then soon-to-be former landlady used to drive me away from enjoying my balcony: she sat in the garden with her acquaintances and talked nonsense in her screechy voice. When that was not enough, she had the trees cut down so that every little breeze would flip the pages of my newspaper. Of course, I could have also given up reading the newspaper and invited friends to talk even more nonsense. Today, I would probably do that too, livestream it, and have followers buy us beers *LOL*

I am not aware of any regulation in the NRW building code regarding a required setback for the terrace (provided it is not covered or raised more than 1.00 m). And since building permits are granted according to the building code and not according to neighborhood law, one will not be able to avoid having to come to terms with this.

Floor-to-ceiling windows alone are not an indication of the presence of a terrace. We are building a single-story house and the only window with a sill is located in the utility room; all others are floor-to-ceiling – also in the bedroom and bathroom ;-)

What exactly do you want to achieve with your neighbor? Stop the construction? No terrace? Just trouble?

I am not aware of any regulation in the NRW building code regarding a required distance from the boundary for terraces (unless covered or raised more than 1.00 m). And since building permits are issued according to the building code and not according to neighborhood law – one will have to come to terms with that.

No building permit was granted for the terrace either. However, it may not be constructed according to neighborhood law. So if the neighbors at some point come up with the idea of building a terrace there, this can be prevented by referring to the neighborhood law. But it is not the building authority that takes care of this, rather the civil courts. It is the same as with a tree that is planted too close to the boundary and is not allowed to stand there.