Preliminary construction inquiry for land purchase: What should be considered?

And to check the possible floor area ratio and plot ratio as well as distance rules and development plans.

That’s not supposed to exist.
But I agree that you have to make sure that with the division, the existing property still has enough land area, and your part also enough, so that you can build what you envision according to the neighboring development in the ratio of plot/house floor area.

It is also not entirely clear to us whether a preliminary inquiry is better made with an architect or whether private individuals can easily do this as well. And regarding the (required?) construction drawing: How is the procedure if such a drawing is not yet available? Are then sketchy details as listed above sufficient? What are your experiences in this regard? :)

So, first step is to contact the building authority and inquire verbally whether this is basically possible?

Nothing works verbally. But to my knowledge, you can simply take the plan, draw a dividing line from the existing property showing what could later be yours, and draw a rectangle there (or two, e.g., for a garage) for the house. A few figures about both new plots and the old one in relation to the built-up areas (sqm) naturally also belong to it (including small calculations). The usual, basically.

I know that a small development area is planned there in perspective. However, we would have the option to purchase a plot in advance.

That would then be option 2 for you? A development area next door does not mean you are allowed to build on the intended plot. The building authority cares that the house fits into the surroundings, also in terms of the size of the built-up area. This concerns sealing, rainwater, and distances on the plot. That is why many municipalities have minimum plot sizes.

If the existing house is very large, the plot size is too small in number, so the calculations are quite tight, then it makes sense to have an architect do it. Because if I already see on the plan that the existing house with 200 sqm ground floor area must keep 1000 sqm of land, but only 500 sqm can be offered to me from a total of 1500 sqm land, and I am only allowed to build over 100 sqm, then this becomes a small task for an architect.
With a total of 3000 sqm no problem.

Normally, it is done by the one who wants to protect his bigger interests. Usually the owner who decides to sell. Because if the project is no longer of interest to you after your building preliminary inquiry, then he still wants to sell and would rather need the preliminary inquiry himself.

I know that a small development area is planned there in the long term. However, we would have the possibility to purchase a plot of land in advance.

P.S.: a new development area does not automatically include surrounding building gaps within its scope – on the contrary: it is not uncommon that plots directly adjacent to the intended scope (and even more so remnants of already developed plots) remain unplanned or even outside the development area. There are numerous threads about perpetual non-developable land just a stone’s throw away from new development areas. Moreover, some hints were given here – including by me with search terms for further research in this forum – and Yvonne also already asked a noticeable follow-up question (my own follow-up questions are sometimes only to be read between the lines), and the original poster was present in the meantime without responding. I find that a pity. On the one hand, forums live from dialogue, and not least from added value for the readers. An open consultation hour with free advice should still bear fruit. Because it is not "free", the advisors invest time for it.

You write that the plot is located in the place where you are already established. That should be enough to know the local prospects. And you write that a residential area is supposed to be created. What you don't write is: what is there now?

Currently, there is a green area. However, our plot would fall within the scope of the resolution to prepare the development plan. Therefore, I assume that the construction can probably be realized according to §34 even without a development plan?

Nothing works orally. But as far as I know, you can simply take the plan, draw a dividing line from the existing development showing what can later be yours, and draw a rectangle (or two, e.g., for a garage) for the house there. A few numbers for both new plots and the old one in relation to the developed areas (sqm) also belong to this (including small calculations). The usual stuff.

That is good to know, thanks.

Would that then be option 2 for you? A residential area next door does not mean you are allowed to build on the intended plot. The building authority cares that the house fits into the surroundings, also in terms of the size of the built-up area. It’s about sealing, rainwater, and distances on the plot. That is why many municipalities have minimum sizes for plots.

That would be option 2 for us, exactly. However, the development might still take quite a while. Therefore, we would favor option 1.

Usually, it is done by the one who wants to protect their bigger interests. Mostly the owner who decides to sell. Because if the project is no longer of interest to you after your preliminary building inquiry, then he still wants to sell and would rather need the preliminary building inquiry himself.

It seems to me that the owner would gladly assign us the task. I find that understandable if we want to have something 'in advance.'

I also find it understandable if we want to have something 'in advance.'

Well ... depending on what is allowed, a property can be sold cheaper or more expensive. It should therefore be in the seller's interest to know what is possible with the piece of land to be sold.

There will be a development plan for the new building area, and it will probably also be applied to your property as part of the resolution to prepare the plan. That would be my assumption.

There will be a development plan for the new construction area, and it will probably also be applied to your property as part of the resolution to initiate the plan. That would be my assumption.

But that would only be an advantage, right?