Problems with the architect

We pay the architect according to HOAI.

It reads as if you are simply angry that you now have additional costs of 1800 that were not planned before.

I rather read it as typical layman misunderstanding. From this perspective, it looks like: it's approved, so check, nothing can be missing anymore. Now the complication guy wants to redraw the plan twice as big so that we give him two grand extra. No wayyy!

You can't know that "who wants to bake a cake must have seven things" is not precise enough for the specific cake, and now the recipe with exact quantities and ingredients is also needed. Only then does the cocktail cherry really come to the middle.

But the site manager should have actually clarified that this is not a pacifier for the architect, but an important basis for implementing the approved plan as desired.

Thanks already for the many answers. Several experts, the structural engineer, the construction manager, told me that a work plan for a small extension would not be necessary. Therefore, I relied on the expert opinion.

Our architect drew this plan without us and without a trade. To my knowledge, details such as electrical wiring, water pipes, and things like that belong there, or am I wrong again?

110sqm is not exactly small. Maybe there was a misunderstanding?

I would not call 110 sqm "small". In an extension, construction drawings are certainly no less important than in a new building - on the contrary: many sources of damage lie in the connections to the existing structure.

Switches and sockets make sense in this, but that electrical cables run in straight lines is sufficiently regulated even without drawings and follows from that. Personally, I have not yet noticed plumbers as great bookworms.

There are many sources of damage in the connections to the existing structure.

I would agree with that.

Personally, I haven't noticed plumbers to be big readers

Documentation of water-carrying pipes is not a bad idea.

Do "we" actually know anything about the details of the extension? The size doesn't matter. What is the construction method (existing and new)? What kind of extension is it, which trades are supposed to work there?

Regarding detailed planning: Do the experts (structural engineer, site manager) already know how the details are to be executed? Will the site manager spend that much time watching the executing people? IMHO: What you save in planning, you have to pay for during execution. I would rather invest in the planning.