Einliegerwohnung - definition question

Does the value of the house not increase due to the potential rent?

To make it short, it's about a single-family house that has always been a single-family house, never rented out with a "granny flat," and that is now supposed to be worth much more than before precisely because of this "granny flat" after an inheritance case.

Doesn't the value of the house increase due to the potential rent?

No, the value of the house is now distributed over two apartments. Previously one house with 200 sqm living space = rented at €10 per sqm = €2,000 monthly. With a granny flat also 200 sqm living space = rented 160 sqm at €10 and 40 sqm at €10 = €2,000 monthly. Which house is worth more? Perhaps this example helps you. Of course, it might currently be attractive for buyers to buy a slightly larger house, where part of it is rented out and this rent can cover a larger portion of the financing due to the interest rate level. But that's about it. If you build a house with 200 sqm, you spend money on 200 sqm (with a real granny flat a bit more, due to a second bathroom, slightly different electrics, etc. – but it's not a huge difference). Why should the house with a granny flat suddenly be worth so much more than the same house where only one household lives alone?

I'm less concerned about the potential rental of these rooms; I'm more interested in the assessment of whether they would be considered granny flats.

And when individual rooms are sublet separately, is that a hotel or guesthouse?
200 sqm remain 200 sqm.
Since a granny flat in the main house does not legally have to be separate (unlike a two-family house), the attic could probably be rented out as a granny flat. But that does not make the house more attractive or valuable, as it is not an independent apartment. Such granny flats are no longer in demand. A kitchen is also not necessary there; a gas stove is sufficient. But who wants that anyway?
A basement, meaning an ordinary lockable basement, must first meet the definition and court rulings regarding habitable rooms. Even then, it is questionable whether a modest rent there would increase the value of the house.
It doesn't read like it would.
Against a small value-increasing rent speaks again the feeling of not being alone in the house, as also says.
Yes, and then there is the target group for these premises in the attic (I’m excluding the basement here): those who can't afford anything else and make do with a gas stove, who like to wash plates and cups in the shower, certainly do not enhance the value of the house.

No, the value of the house is now divided into two apartments. Previously one house with 200 sqm of living space = rented at €10 per sqm = €2,000 monthly. With a granny flat also 200 sqm living space = rented 160 sqm at €10 and 40 sqm at €10 = €2,000 monthly.

Which house is worth more? Maybe this example helps you.

Well, rent pricing is somewhat more complex. You cannot rent a 200 sqm apartment at the same price per square meter as a 150 sqm apartment or vice versa. Keyword: diminishing marginal utility. At the same time, the granny flat can of course have a positive or negative effect. In my opinion, the rentability will definitely have a positive effect on the bank’s willingness to approve a loan.

Ultimately, it is a very individual consideration that mainly depends on how the housing market is structured where you are: There are people who say, oh wow, with the apartment I can pay off the house more easily. On the other hand, there are buyers who say, uhh no, I buy a house precisely so that I don’t have a stranger living in it.

To add something to the original question: I would only advertise the apartment as such if it actually comes close to a full-fledged apartment. That is definitely not the case in the basement. In the attic, this could possibly be achieved by installing a kitchenette. Whether it can then be rented out “profitably” again depends on whether the apartment with its features fits the demand on the housing market where you are.

Example Rhine-Main / Frankfurt metropolitan area: Here you can earn a golden nose even with a sparsely furnished studio with a kitchenette. In regions with less housing scarcity and willingness to pay, it may look different.

Thank you for your answers, that already helps me a lot.

As I said, it's not about increasing the value of the house; I have no intention of renting out the "Einliegerwohnung." Rather, my goal is to gather arguments that demonstrate that it is not an Einliegerwohnung as the opposing party claims, and thus massively raises the value of the house.

No landlord who is reasonably sane would rent out these rooms, as his own rooms and all his valuables would be freely accessible. Not to mention the privacy that would be lost.

If this apartment had a completely separate entrance, then it would be a two-family house, regardless of how big or small this apartment is?

Since I have recently started working in this field, namely the consideration of the property market (no, not a real estate agent or anything like that), I can contribute that among appraisers it is generally assumed that a house with a granny flat is worth about 10% less compared to a house without a granny flat (all other conditions being equal). However, the fact is that in individual cases it can always look completely different!