Link property purchase to future buildability?

I am looking for a way for us as property buyers to transfer the risk that a development according to our plans may not be permitted later to the seller.

The crux with the specific property is a building boundary (boundary between inner and outer area) that parts of the building would have to exceed for the building to be sensibly placed in the planned size. There is no development plan (according to surrounding development, §34).
There are already positive statements from the municipality or building authority that this is acceptable (by email). However, I suspect that one probably cannot rely on this in case of doubt?

As far as I am informed, a legally binding statement is only available through a preliminary building inquiry – but unfortunately I am still missing the detailed planning of the building for this.

Therefore, I am considering including a clause in the notarial contract that the purchase is only subject to the condition that a building with minimum dimensions of X x Y, two full floors, and a lateral distance of X meters from a certain property boundary can be constructed later.

Is something like this conceivable? Would a cancellation of the purchase or reversal even be possible in practice? Presumably at least the incidental purchase costs would have to be paid?

I would appreciate your opinion or perhaps even experiences from similar situations.

Not finally checked but in principle you could have a suspensive and/or resolutive condition (§158 Baugesetzbuch) included in the contract. Depending on what you decide, in the case of a suspensive condition, the contract only comes into effect, for example, upon the granting of the building permit.

The biggest hurdle I see is with the seller; why should they agree to something like that? As long as the suspensive condition is not fulfilled, it still belongs to them and no money is paid.

Is the demand so high that a reservation is being sought through this route? Would the seller not be willing to give you the chance to make a preliminary building inquiry because they could sell it to someone else in no time?

I see two scenarios:
- Demand very high: Seller has no reason to agree to such a clause
- No demand or urgency to sell: Talk to the seller, perhaps they will give you the time to make a preliminary building inquiry. This is definitely easier than working with such a clause.

It should be considered that, depending on how many other interested parties there are for the [property], I would find that too annoying as a seller and would rather wait for the one who buys without conditions.

Addendum: If there are no plans, which condition should then be included in the notary contract? "I only buy if the building authority approves any wishes I have now or in the future?" Exaggeratedly expressed, of course.

I am therefore considering including a clause in the notary contract stating that the purchase is only valid under the condition that a building with minimum dimensions of X x Y, two full floors, and a lateral distance of X meters from a certain property boundary can later be built.
Is something like this conceivable? Would cancellation of the purchase or reversal in practice even be possible? Presumably, at least the ancillary purchase costs would have to be paid?

Common practice in commercial transactions.
Here, a positive preliminary building approval could already suffice. For that, you don’t need a very concrete plan.

In the private sector, however, I would send you to hell with your wish. Why should a seller agree to that when land is scarce? Unless you live at the AdW, where there is no demand.
But asking doesn’t cost anything.

In principle, it is quite possible, we have agreed the following in the notarized contract:

If this buildability is not given, the purchaser can withdraw from the contract, but may not demand a reduction of the purchase price (abatement) or damages. The right of withdrawal expires on XX.XX.XXXX; however, it is extended until XX.XX.XXXX if a successful objection has been filed against the aforementioned supplementary statute. For the exercise of the right of withdrawal, the following applies: It must be made in writing to the seller; the timeliness is determined by the receipt by the seller.

It should be noted that the seller proposed this; we did not insist on it.