Bavaria: 2 single-family houses or a duplex?

I'll start with the question from your headline: by joining the two units side by side, you save two side building gaps, thus potentially "gaining" six meters of usable plot width in exchange for one window side per unit. What you directly save in connection with this sticking together of the two units in terms of money, we're talking about eighty-five pfennigs, if at all. Almost "more spiritual, you know," to quote Monaco Franze ;-)

Being able to and being allowed to are at least two different things, so you should definitely look at the development plan. We are also happy to help you interpret it – caution! you are not allowed to link it here (but you can name it, e.g. "Hintertupfing No. 258 am Rübenacker"). You are talking about one plot for two single-family houses – they must not only have space there but also be allowed there.

You have hopefully already read that "prefabricated" houses are neither more finished nor more budget-secure (but also not less solid than stone-on-stone built ones). The commonality of most pub myths is their often scant truth content. However, I do like the approach that you want to make "as few changes as possible," because that is the best way to succeed with a standard house design.

Regarding your question number 0, which you only added here afterwards...

If it should be 2 single-family houses, does it make sense to build them at the same time? Or is it maybe even better to build one after the other to learn from potential mistakes...

...you will find in numerous threads here under the keywords for forum search "With basement"/"Without basement" and "Goalkeeper thread" explained warnings why in the case of a semi-detached house secondly the planning should be done jointly and firstly the straight arrow path to disaster would be if the one without basement builds before the one with basement. By the way, in case the decision goes towards the semi-detached house, I recommend my (external) contribution "A semi-detached house has TWO halves," see "building now." The difference between the two units is unproblematic except for the basement aspect (see the keyword "11ant basement rule," which the plot also has a say in), but the profile at the "seam" of the two halves is also critical.

Thank you again for the further explanations! Then I will fill out the questionnaire as far as possible:


Development Plan/Restrictions
Size of the plot: 1,200 m²
Slope: no
Development plan: like the neighboring development. The neighboring plot was also separated and will be built with 2 single-family houses or even 1 single-family house + a semi-detached house
Plot ratio: like neighboring development (mainly single-family houses and semi-detached houses)
Floor area ratio: like neighboring development (mainly single-family houses and semi-detached houses)
Building window, building line and boundary
Edge development
Number of parking spaces: 2 per single-family house / semi-detached house
Number of floors: 2.5
Roof type: gable roof


Requirements of the builders
Number of persons, age: 2 persons, 1 baby (reserve for 2 more children)
Living area: 170 m²
Office: family use or home office: home office 50%
Open kitchen, cooking island: no, closed kitchen
Number of dining seats: 6
Balcony, roof terrace: possibly balcony on the 1st floor
Garage, carport: garage
Utility garden, greenhouse: no
Other wishes/special features: From the 1st floor and especially the attic, there is a nice view. This should somehow be utilized


House design
We do not have a design yet.


My question: What budget should I roughly plan for this? Do you have a supplier of prefabricated houses in mind that would be suitable (southern Germany, house with 2.5 floors, mid-price range)?

We are here in the official forum of cross-ventilation and it was even speculated that there might be a legal obligation for this – so with a semi-detached house it already becomes more difficult, because creating a draft through the other half of the semi-detached house is tricky. Whether in 2023 you still have to ventilate a multi-story house through cross-ventilation window openings is another matter.

Seriously: I am currently considering something similar, but on a smaller plot. My thoughts were/are:
- Is the soundproofing really as good as if they were two independent houses?
- Do I want to do without windows on an entire side of the house?
- Will the larger contiguous garden area that I gain through the semi-detached house actually be used by both parties?

But above all: Do I really want to bind both houses together?

Sure, everything is technically possible but if they are two separate houses, then I imagine any changes would simply be easier. As long as a builder constructs both parts for themselves and builds them identically, everything is fine, but maybe one wants a huge cantilevered ceiling, then the ceiling has to be stronger, then the ceiling in the other half of the house also has to be thicker... so I really imagine it would be difficult in the planning phase if on one side someone says "I'd prefer it like this" and that has an impact on the other side.

For me, I now only see the matter of the set-back areas as an advantage for the semi-detached house because then I don't have a narrow and practically useless strip around each house.

With 1200 sqm and rectangular shape, you can definitely work with individual houses. That's basically the level of today's new development areas.

My question: What budget should I roughly plan for? Do you have a provider of prefabricated houses in mind that would be suitable (southern Germany, house with 2.5 stories, mid-price range)?

Depending on the standard, €3000-3500/sqm, of course open upwards. You can basically take any provider from the mid-segment, you just have to compare. I wouldn't pin myself down to prefabricated houses either. Catalog prices usually differ significantly from the first concrete offer and it's not worry-free all around.

Then I'll fill out the questionnaire so far:

We probably need to practice this a bit more: a "development plan" does not mean what type of development you plan for the property, but what development the authorities allow there. You can usually find this official development plan already linked on the municipality's website (as mentioned, please DO NOT link further here, but state its name). It will show, for your property or building plot, for example in a usage template, which floor area ratio and floor space index are permitted. Also here, it does not mean the number of floors, but the footprint of the house in relation to the property, and the sum of the floor areas of the stories. For example, a floor area ratio of 0.2 and a floor space index of 0.4 would mean that on a 1200 sqm property you may build 240 sqm of ground-floor slabs and 480 sqm of living and usable space (simplified). A "II" would then allow you two full floors, and so on.

Now check the development plan (only where there is none - which practically never applies to new building areas - the insertion requirement according to §34 Building Code applies), and add a screenshot from the cadastre here; the keyword "Bayernatlas" should help you further.

I think 1200m² in the outskirts of Munich and the neighboring plot already being divided strongly suggests infill development/densification and that it is indeed a §34 case. But let's wait and see...