Bungalow - does it make sense on a plot like this?

with max. approx. 70 cm knee wall

only 70 cm left? Then dormers everywhere, until nothing else is possible Seriously: parent area on the ground floor, then that is all sufficient.

Thank you very much in advance for the initial comments.

Yes, the information comes from the development plan. Which, as a layman, I find terrible, by the way, but I will try to answer all open questions. Regarding the measurements, I can't say much except what I also see in the excerpt. After reviewing, my father-in-law said the possible building area would be 15m x 15m. But if we come to a conclusion about the feasibility here, I would make an appointment with the building authority anyway.

The floor area ratio is 0.4. We would aim for about 140-160 sqm if we could realize additional storage space in the form of a basement. I actually did not consider the attic as a bedroom under the specified requirements. I admit, it's also hard for me to imagine something there – that's why I'm asking you. A garage already exists, and a car is definitely available.

About the plan itself: the blue-red area is the building window, yes. The plan is oriented north. Access is only possible via the street at the top (i.e., to the north). To the right on the property boundary, there is another house directly adjacent.

Going upwards... as I said, I thought that would make little sense. Regarding the dormers from the textual stipulations:

Dormer windows are permitted up to a maximum of 1.10 m above the finished roof surface. The minimum distance from the verge is 1.50 m for detached houses as well as for semi-detached and terraced houses from the free-standing gable. The maximum height of dormers measured from the upper edge of the floor to the lower edge of the dormer ceiling is 2.00 m, but no more than 1.10 m above the finished roof surface.

So better keep distance from the combination of "this property" and development plan requirements? The square meter currently costs 390 euros.

Nordlys showed you the "basement" and if you Google Schwörerhaus Plan E15-244.1, you will see a developed variant.

Just google houses with gable roofs up to 70 cm knee wall. Check out all the big companies.

I wouldn't say the plot is no good. What are the alternatives?

What is your space requirement = approx. sqm number?

Apart from the bedrooms? Office? Etc.

I can't say much about the dimensions, therefore

That wouldn't be so bad either, since there are a few measurements included and one could measure oneself. Unfortunately, you chose the excerpt so that either the reference points are cut off or the text was painted over illegibly.

Father-in-law said after inspection, 15m x 15m

The construction area doesn't look square. I guess it's 16m*14.5m. With a plot ratio of 0.4, there's enough space, even for a bungalow. Whether that makes sense here and fits into the still unknown budget might still be determined.

not intended as a bedroom.

How about children's rooms? Here too, a potential advisor misses the completed questionnaire. Small children play on the floor, so somewhat lower sloping ceilings are insignificant.

Regarding the plan itself: the blue-red area is the construction area

Red is usually a building line on which you must build, blue the building boundaries which must not be exceeded. Maybe there's a legend confirming that.

Right on the property boundary there is another house directly adjacent.

The garage or the residential house? In the latter case definitely look up the register of building encumbrances (Well, you should do that anyway). Is it attached to the rundown existing building?

Going upwards ... as I said, I thought that makes so little sense.

With a 30° roof pitch and a clever floor plan, that can be very sensible. Especially if you want to have some garden left. Is the ridge direction predetermined? The roof shape? What about the neighboring properties? Only bungalows?

So rather distance from the combo "this plot" and development plan requirements?

The development plan is estimated to be from the 60s. So some exemptions should be possible. So take a look around the area and don’t hesitate to make an

appointment at the building authority

So better keep distance from the combination "this plot" and development plan requirements? The square meter costs 390 euros according to the current status.

That would probably be my clear favorite. Although you see little in the drawing, I immediately don't like a lot: I see embankments and wonder at how unfavorable a position the max. 30 cm base might be measured; I see a probable building window and a building line, in front of which an existing garage is off to the side – without an additional "Ga" building window for its successor. It doesn't seem to me that this is a development plan from the 60s, but a new development plan that derives the building windows from the existing main buildings in a 34er area developed in the 60s. Therefore, what I mainly take from this plot offer is: keep distance. I think being near Cologne also explains the price. Besides, the house type "bungalow" does not seem to me the first choice for a classic full family; bungalows for more than singles or couples (without or after children) need in my opinion more plot (or at least more building window).