Developer New Build: Buy two apartments and then combine them

Well, you can back out at any time up until your signature at the notary appointment. In case of doubt, he then ends up with differently divided residential units and the costs of the new partition declaration on his hands. For you, a subsequent change is bad because you pay for the new partition declaration from taxed income. For the developer, it would be operating expenses. Maybe a regulation can be found where he covers the change of the partition declaration and you pay him, in return for the merging, a surcharge on the purchase price corresponding to his net costs.

Yes, that also sounds like a significant reason why the developer proposes it that way. However, the "surcharge on the purchase price" doesn’t help the developer with the risk that we could still back out at any time before the notary appointment (if that is his main problem). But maybe some kind of "pre-contract" or similar could be made so that we don’t back out ;-) In any case, from my point of view, the whole thing would still be cleaner and especially safer for us if we really buy the merged unit at the notary appointment without all the after-the-fact changes.

You hopefully are not harboring false hopes of being able to realize a differently divided house within the "two-family house" corpus by reworking the construction plans. In any case, I see it remaining with two "separate" floors; of course, you can omit the apartment doors, only carry out pre-installations in one of the two kitchens, and have the parents' and children's bathrooms stacked. If I were you, I would
- do it this way if the homeowners' association (WEG) refers to the "two-family house" (such a small WEG can be self-managed), but
- not do it if the WEG level refers to the overall project.

But the "surcharge on the purchase price" does not help the developer with the risk that we could back out at any time before the notary appointment

Yes, it does! Your purchase contract states purchase price + X (additional costs) and obliges the developer to subsequently adjust the declaration of division according to the plans attached to your purchase contract. Preliminary contracts related to real estate are at least critical, as under strict legal interpretation they also require notarization.

Hopefully you are not getting your hopes up to realize a differently divided house within the "two-family house" corpus by reworking the building plans. In any case, I see it remaining two "separate" floors; of course, you can omit the apartment doors, only perform a preliminary installation in one of the two kitchens, and have the parents' and children's bathrooms above each other. If I were you, I would
- do it like this if the homeowners' association (WEG) refers to the "two-family house" (such a small WEG can be self-managed), but
- not do it if the WEG level refers to the entire project.

Essentially, the "united two-family house" (from the two apartments A and B) then looks just like the other row houses in this development – only larger because it is wider. Viewed from the outside, it is thus a row house block with 6 units, of which "our" unit would simply be larger than the other 5. The layout then basically follows the other row houses, just everything a bit larger.

Yes, it does! Your purchase contract states purchase price + X (additional costs) and the obligation of the builder (BT) to subsequently adapt the declaration of division according to the plans attached to your purchase contract. Preliminary contracts related to real estate are at least critical since, in strict legal interpretation, they also require notarization.

Understood! Such a clause of obligation would indeed not be a bad idea. Presumably, it would also need to regulate what happens if the building permit for the modified variant is not granted or if the other co-owners do not agree to the change of the declaration of division.

If I were in your shoes, I would [...] not do it if the level of the WEG refers to the entire project.

Subsequently, in May, we are to sign the notarized purchase contract for both apartments. Afterwards, the developer takes over the combined planning into the construction planning and creates a Tektur (amended building application). After the Tektur has been approved by the building authority, an updated certificate of completion is created and subsequently the declaration of division is amended.

That unfortunately speaks in favor of a double condominium within a large WEG. You can email me the link to the specific project, and I will gladly take a non-binding look at it.

if the building permit for the modified version is not granted or the other co-owners do not agree to the amendment of the declaration of division.

For the failure to grant the building permit, I would then have a right of withdrawal and assume the costs already incurred (because you have already paid the notary). Usually, the BT have a power of attorney to make changes in the notary contract (check if this is stated in your draft) that allows them to still change the declaration of division during the construction phase. Legally, this must not lead to a reduction in value of the other residential units, but in your case, it wouldn't be like that anyway.