Buy a house when the floor area ratio is exceeded?

What are the consequences? - Fine?

Yes.

How much?

Triple building permit fee.

- Demolition?

Yes.

What can you do?

Take it or leave it.

- Chance for official approval?

Facts? Age of the development plan? Comparable cases in the neighborhood? Political composition of the municipal council? Workload of the building authority? Character of the caseworker/department head? ...

What would you do?

Negotiate down.

Would you forgo the purchase because of something like this?

No.

Or am I exaggerating and in the end no one cares anyway?

I can’t find my crystal ball right now. Hitting the jackpot in the lottery is very unlikely, yet some people manage it every year. Would you take AstraZeneca?

A house like that doesn’t sell so well without a terrace either

If you’re already thinking about selling, forget it.

I wanted to refer to my essay from 01/21/2019:

Terraces are a controversial topic

Facts? Age of the development plan? Comparison cases in the neighborhood? Political composition of the municipal council? Workload of the building authority? Character of the caseworker/office manager? ...

I had written, the development plan is from 2006 or so – so in no case old enough for the terrace not to count. I looked at a few neighboring properties on GoogleMaps, that seems to fit better. I haven't found any significant exceedances at least. The political composition of the municipal council is unknown to me and also subject to change. I (still) do not know the character of the caseworker.

In our construction area, there is probably something on every plot that does not comply with the development plan and was probably not approved either. If someone now had to dismantle a terrace because of exceeding the floor space index, then the other neighbor would have to remove their tree that is not in the planting plan, another the driveway that is too wide would have to be shortened, and the other neighbor would have to remove the embankment that is 20cm too high. Etc. Etc. ....

I had written that

Yes, sorry, I read that and then saved it incorrectly.

so in no case old enough that the terrace wouldn’t count.

But old enough to not exclude an exemption.
If you are so unsure about the terrace, you surely took someone from the field to inspect the building. How does he assess the situation?

The political composition of the municipal council is ... well, also changeable.

Exactly. If climate and environmental protection gain importance on the local agenda, this can certainly have an impact on administrative actions. Still, if you don’t exaggerate, e.g. build a large garden house, a wood storage shed, a solid grill pavilion, a pigeon loft, a small animal enclosure, professional playground equipment, and a greenhouse, the administration won’t bother starting a regulatory enforcement procedure over a 0.08 exceedance.
IMHO unlikely, but conceivable: Subsequent legalization through an application for isolated exemption. Costs including architect approx. €5000. You can do that if indeed a dog has woken up.

Would you take Astra Zeneca?

Yes, I have and I'm still alive! That's why I would also buy the house. The comparison would probably be "not buying a house because of the terrace" and "getting Covid-19".....