Extension of a 1960s house and energy-efficient renovation

Hello everyone,

the existing building was constructed in the 1960s. Over the years, renovation work has repeatedly been carried out on it (electrics, windows, floors on the ground floor, staircase ...). However, the electric heating is an energy guzzler. The rooms are small and the current layout is no longer suitable for 2 households. On the north side, a garage stretches along the entire length of the house, hidden on a half-floor between the basement and the ground floor.

The idea:
After much consideration, an extension of the existing building towards the southeast seems sensible to us. This would create a building with dimensions of 14x9m (existing 8x9m + extension 6x9m = 126 sqm floor area). Ultimately, two separate residential units are to be created. A utility room for each apartment is mandatory. Additionally, it would be good if the apartment on the upper floor could also use the attic as living space. This can certainly be designed openly, but I lack the imagination regarding the layout. I also don't know to what extent the exterior wall of the old building will prove to be problematic for planning. It will certainly have to remain standing in any case.

The crux with the existing building is that you have to walk all the way around the house to reach the entrance door (west side). To prevent guests to the upper floor from having to pass by the ground floor, the entrance area should be directly accessible from the street (south side). The only question is: what to do with the existing staircase? Demolition is difficult since it provides access to the basement. Should the old entrance remain for the ground floor and only the upper floor get a new entrance from the south side? I am undecided. I do not necessarily want to cellar the extension – primarily for cost reasons, plus the existing basement is actually large enough.

Technology:
I would like to replace the old electric heating with an air heat pump with underfloor heating. The roof covering will soon be due for renewal. If you build an extension, the roof has to be redone anyway. In this process, one could also consider a photovoltaic system. In addition, new windows will be installed everywhere and the exterior facade must be insulated. Does it make sense to build the extension with built-in insulation right away? How is the best way to insulate the old building?

What does the development plan say?
Type of structural use = "general residential area"
Plot ratio = 0.3.
However, the permissible floor area of structural facilities may not exceed 200 sqm per single house or 100 sqm per semi-detached house (the floor area of the main structure without terraces and balconies is decisive).
Floor space index = 0.6 (max. 2 full stories)

For buildings with gable roof (SD), hip roof (WD) or pyramid roof (ZD) the following applies:
- maximum ridge height (FHmax) 10.5 m
- maximum eave height (THmax) 7 m
For buildings with flat roof (FD) or shed roof (PD) the following applies:
- maximum height of the top edge of the building (OKmax) 7.5 m

Roof pitch for gable/hip/pyramid roofs = 25–40 degrees
Roof pitch for shed roof = max. 10 degrees
Semi-detached houses as well as semi- or row house-like single houses must be built with a uniform main ridge direction and uniform roof pitch.
Roof structures and indentations such as dormers, cross gables and loggias are permitted if their total width per roof side does not exceed half the width of the exterior wall below. The width of cross gables may not exceed one third of the width of the exterior wall below per roof side.
The height of dormers and cross gables (measured from the top of the raw floor of the attic to the top of the dormer/cross gable roof) as well as roof indentations may amount to a maximum of 75% of the total height of the roof (measured from the top of the raw floor of the attic to the top of the ridge).
Dormers and roof indentations must set back at least 0.5 m behind the outer edge of the exterior wall below.
Roof structures and indentations must keep a distance of at least 1.25 m from gables, ridges or valleys, measured at the narrowest point.
The viewing surfaces of dormers must be designed as windows.

Well, now I hope for one or the other idea. The project is still in the design phase. I am open to all suggestions.

Best regards
Sven

Hello everyone, I have given further thought to the floor plan. Attached is the draft of the upper floor. The entrance is on the east side. In this case, access would be via an external staircase. Access to the ground floor remains unchanged, as does the staircase in the northwest. The old bathroom and the old hallway must make way for a new dining area. The new bathroom is located in the annex and is also accessible from the bedroom. The bathroom also houses the washing machine and dryer, making a utility room unnecessary and creating more space for a children's room. I think it should be at least 15 sqm in size. In addition, there is an attached balcony on the west side. The attic is accessible via the existing staircase and would be available as expansion space. What do you think about that?

A floor plan that is even more outdated in its layout after an extension than in the original year of construction - who is supposed to find that attractive to rent?

To be honest, it is not intended for rent

And why two separate units?
By the way, it would be better to upload jpgs here, unfortunately I could only open the OG, and with this hallway pipe it already looked very uncomfortable.
Have you ever measured how wide a grown slender person is? Measured from knuckle to knuckle, so that you don’t scrape the textured wallpaper on the walls with them?

Best regards in short

Hello, first of all thank you for the constructive contribution. The 2 units result from the fact that my mother lives in the house and my wife and I want to move into the upper floor. The original plan to build another single-family house in the rear area of the property is thwarted by the development plan.

I am also not really happy with the narrow corridor. It is wasted space, especially if you make it wider. At this point, I am somewhat out of ideas. The annoying thing is the exterior wall of the existing house. It simply gets in the way of large and open rooms.