ᐅ Two-family house with two owners

ypg schrieb:

It would also be interesting to consider the worst-case scenario, where the domestic hot water tank gets emptied quickly on one side due to heavy usage.

However, this issue occurs in every multi-family building as well.

ypg schrieb:

It would also be interesting to consider the worst case, when the hot water storage is emptied on one side due to a lot of bathing..

That is not really a worst case. For example, a 9 kW heating element is installed in the 500-liter (130-gallon) tank, which switches on at 45°C (113°F) using a thermostat. The only "issue" is the electricity consumption – but that is known in advance. (These are only theoretical figures and must be designed according to actual usage and planning.)

The topic becomes more interesting when this is combined with the (usually legally required) photovoltaic system... or if one opts for full feed-in.

Musketier schrieb:

But this problem applies to every multi-family building as well.

That's true. But when I rent an apartment somewhere, it feels different than building something of my own. In multi-family buildings, electric tankless water heaters are also often used.

Musketier schrieb:

With that, you would basically end up creating a semi-detached house, which is prohibited according to the development plan.

There is no outright ban; the development plan regulates the use. But you are right in the case of having two entrances and the obvious semi-detached house situation.

I am not aware of any rule that forbids building a semi-detached house on a single-family house plot when divided virtually. Usually, it’s the other way around: semi-detached house plots can be designated smaller than single-family house plots (for example, 400m² (4,300ft²) versus 650m² (7,000ft²)). However, this is usually bypassed through virtual division.

The savings are just a few thousand dollars on the technical equipment, and that comes with some drawbacks. The parking space regulations would also be an interesting aspect to consider.

Waldrich schrieb:

I’m curious if anyone has ever carried out a similar project. We have several questions in mind regarding the division plan, certificate of segregation, and declaration of division.

I’m not sure yet if and when @i_b_n_a_n will respond to my invitation to contribute here. However, that doesn’t mean the meantime should be used to shake up a cocktail of a few basic facts and various resulting misunderstandings. So let’s stick to the facts:

Waldrich schrieb:

My girlfriend and I are planning to build a two-family house together with a couple of friends.
The individual living units are not stacked but arranged side by side in two equally sized sections, each with its own front door. From the outside, it looks like a semi-detached house with mirror-image halves. Each half extends over two full floors plus a converted attic. Inside the house there is a shared utility/technical room, which must be accounted for equally when deducting from the respective living areas and is accessible from both sides through a door.
There is a single heat pump serving both halves.

So, two couples (with uncertain parallel family planning) and a plot of land that would not allow a semi-detached house even after subdivision. That’s a fact, which forces a purely virtual division (recommended as a condominium ownership, also called strata title or community title) as a two-party house. Combined with separate financing, this leads to the legal form of condominium ownership as a further practical necessity. Separate land parcels are not required for the ownership shares; besides (not necessarily symmetrical) semi-detached forms, a classic two-family townhouse arrangement (for example, with the utility room in the attic) would also be possible. At this point, I’d like to throw in a hypothetical test for the friendship by asking: who would give the other priority in a coin toss over who sleeps upstairs?
That a shared “combined heat and power system” (or a similar shared heating system) would suffice for both units is also an economic fact and quite reasonable, and therefore will remain the plan. Behind this, separate meters can be installed for both parties as in a typical multi-family house. Reserving a blind second technical room for splitting the joint facility later seems excessive to me. How the shared technical center is managed can basically be decided by the owners’ association. To avoid a deadlock, I recommend allocating voting rights according to the exclusive usage areas. In practice, this could be done by arranging the utility room (or if mainly located in the attic, the house connection room), so that the share of the unit closest to it is effectively reduced in size. For example, if the attic utility room is 10 sqm (108 sq ft), and the ground floor house connection room 3 sqm (32 sq ft), with apartment A having 97 sqm (1045 sq ft) and apartment B 100 sqm (1076 sq ft), and a garden for common use, this means that co-owner B would have 100/197 voting shares and could decide in case of dispute. Is the friendship still stable at this point in the text?

ypg schrieb:

It would also be interesting to know the worst case if, for example, one unit empties the hot water storage by taking many baths…

Musketier schrieb:

I would be a bit surprised if the building permit for separate utility rooms passes. That way, you would ultimately create a semi-detached house which is prohibited by the development plan.

Musketier schrieb:

But this problem also applies to every multi-family building.

As long as exclusivity is maintained (each unit must have a cooking facility and a toilet), the rest of the house can be fully used for house connection rooms. Also, multiple meters can be added to hot water tanks. And I have not heard of a single case where, in one of the countless six-family buildings divided into condominiums, a majority co-owner forced the others to install their own heating systems or disconnected them from the shared heating supply. The residual risk of a lunar eclipse on a day that never comes is negligible. Therefore, besides taking precautions, buying extra insurance for hypochondria—as in overdoing it—is also an option.

ypg schrieb:

There is no ban; the development plan regulates usage. But you are right in the sense of two entrances and the obvious semi-detached house. I don’t know of any plot designated for a single-family house that does not allow a semi-detached house to be divided virtually. [...] The parking space regulations would also be interesting.

Virtual division or condominium ownership, no development plan limits the number of entrance doors. Probably two residential units per plot are permitted here, and the aim is to avoid four units (which would require 6 or 8 parking spaces) on the property.

So: communicate openly, do the “bunk bed test.” Depending on the outcome, either lean towards building a classic two-family townhouse or opt for a “virtual semi-detached” arrangement. Either way, in line with my warning about deadlocks (there is hardly a way to avoid condominium ownership here due to financing), create a slight asymmetry in voting rights—in my example, the party giving up space for the shared utility room would also have to accept being outvoted—or provide a redundancy reserve for a potential second technical room. You will have to accept one way or another that you cannot wash without getting wet.

---

https://www.instagram.com/11antgmxde/
https://www.linkedin.com/company/bauen-jetzt/

I have done something very similar to what you are planning and am currently finishing the construction of the project. My brother and I owned a plot of land together. Since my brother is single and didn’t want a whole house by himself, and I already live in a property with my family, the idea of a two-family house came up. We had an architect design a two-family house with two living units of 106 and 108 square meters (1141 and 1163 square feet). Additionally, there is an attic that can be converted into a smaller apartment.

The architect submitted the building permit / planning permission application, but since the design didn’t fully comply with the zoning plan, there was some back and forth with the local authority. Eventually, it was approved. Only after the permit was approved did we take care of the declaration of partition. I did that myself and manually adjusted the architect’s plans as needed, depending on what the local authority requested (elevations with and without garage and all kinds of other details). In hindsight, it would probably have been wiser to have the architect handle this from the start.

After the declaration of partition was approved, we went to the notary and had the division agreement drawn up. Only then did we arrange financing. For example, Commerzbank, which offered me the best terms, was unwilling to finance my part. They only wanted to finance the entire project, not the construction of one condominium unit. However, we wanted to finance separately since I am renting out my unit and my brother is moving into his. So, I financed my unit through the local savings bank, and my brother through a cooperative bank.

We also have a shared utility room/technical room with a common heat pump including a domestic hot water tank. Of course, each unit has its own heat quantity meter and electricity meter. The heat pump has a separate meter as well. General electricity is measured via a submeter. Garage power supply and electric vehicle charging stations are also assigned to the individual units.

Exclusive ownership, for example, includes the ground-floor terrace. Regarding photovoltaic systems (not mandatory in Bavaria), my brother is installing panels covering the entire roof for his unit. I’m not interested in photovoltaics because I don’t want to deal with tenant electricity issues. Parking spaces were also a topic. We had to provide proof of four parking spaces: a double garage plus two additional spaces, which are not allowed to be in front of the garage.

These are just some of the things that came to mind.

ypg schrieb:

Yes, good idea. Still, people might not view the worst-case scenario (“hey everyone, we’re renting out because we’re moving and want a change”) positively and it could potentially cause conflict.

Absolutely; just returning from a summer walk, I wanted to tell @Waldrich that I would rather advise against it, not only because of my own experience, which of course is just one case. Technically, it’s one thing, but interpersonally it’s much more unpredictable.
I’m a fan of maximum freedom but also really appreciate genuine joint projects. In this idea here, I don’t see any significant advantage besides a certain amount of money (which still needs to be calculated). There are plenty of problem areas.
You have a long friendship but with a healthy distance, which I would also like to maintain. When entering a new kind of relationship, problems almost inevitably arise, like in a marriage, and being emotionally tied up in that can become very stressful. Building something together, yes—but only as a semi-detached house or one person builds the entire property and rents it to the other.
Just because the building plot allows it, I wouldn’t want to force myself into that and would rather look for other options.
The savings you make, if any, in terms of square meters and money overall are very small, so based on experience, I would never take that risk. Look up Loriot’s “Kosakenzipfel” sketch, as he didn’t invent those topics but always took them directly from everyday life.
For example, with a semi-detached house, there’s just as much potential to save money through car sharing, shared lawn mower, tools, household appliances, or even a DSL connection, and all of these can be separated again if needed; that’s not the case with this kind of living arrangement.
There are plenty of examples of both successes and spectacular failures, but ultimately, everyone has to decide for themselves.