Extension planning for house from the 60s

Hello,

we are planning in the mid-term to replace the existing conservatory at our house with a new extension. So far, we already have a few ideas, but we still have time. However, we want to keep the goal in mind in order to, for example, complete necessary preliminary work or avoid obstructing ourselves in any way.

As an introduction, I use the questionnaire for regular floor plan planning as far as possible, although many answers naturally reflect the current state:

Development plan/restrictions

[*
Size of the plot: 787m²
[*]Slope: no, only slight gradient
[*]Floor area ratio: 0.2
[*]Floor space index: 0.3
[*]Building window, building line and boundary: see development plan, the north side of the building is the building line, otherwise approximately twice as much may still be built
[LIST]
[*]Development plan (1st amendment) (colored)
[*]Development plan (2nd amendment) (changes not relevant, but somewhat easier to read, black and white)
[*]Excerpt from development plan (oriented to north):

35273[/ATTACH]

[*]Edge development: actually not, however, according to the development plan the entire garage/patio is within the building window and may be fully built as I WR
[*]Number of parking spaces: Current: driveway offers space for 2x2 cars and 1x garage, Desired: 2 parking spaces (in a double garage)
[*]Number of storeys: 1 (I WR)
[*]Roof shape: gable roof, knee wall 108cm
[*]Architectural style: original state elements of Heimatstil, modified standard model of Niedersächsische Heimstätte in improved version/equipment
[*]Orientation: balcony/terrace to the south
[*]Maximum heights/limits: no requirements
[*]Further requirements: development plan imposes no restrictions

Requirements of the builders

[*]Basement, floors: 1 basement, 1 ground floor, 1 upper floor (partly sloped ceilings), 1 attic
[*]Number of persons, age: 2 (35 + 37)
[*]Space requirements on ground floor, upper floor
[*]Office: home office + guest room
[*]Annual overnight guests: 4 times 2-3 persons each
[*]Closed architecture
[*]Conservative construction with modern elements (matching house type)
[*]Closed kitchen
[*]Number of dining places: breakfast place in kitchen, dining area in living room
[*]Fireplace: planned for living room
[*]Music/stereo wall: TV with 7.1 sound available
[*]Balcony: existing, but unnecessary
[*]Roof terrace: no
[*]Garage: existing, too small, target: double garage
[*]Carport: no
[*]Utility garden: yes
[*]Greenhouse: no

House design

[*]Who designed the plan:
[LIST]
[*]Original is a prefab house type from Niedersächsische Heimstätte
[*]but built in Wolfsburg for the middle class in the 1960s
[*]with modifications compared to standard (bathroom with bidet [otherwise children’s room], additional shower on upper floor [otherwise bathroom], additional WC on ground floor, only one chimney flue due to district heating supply, real wood parquet)
[*]Around 1995 a conservatory was added on the terrace (balcony extended with bitumen roof)
[*]Patio roof was extended and front closed with glass sliding doors
[*]Facing brick slips on two sides of the house, ETICS on the other two sides

[*]What do you particularly like? Why? Compact and not too large, still some 60s flair but not outdated
[*]What do you not like? Why? Living room too dark due to conservatory, partly too narrow for sensible furnishing
[*]Price estimate according to architect/planner: n.a.
[*]Personal price limit for the house, including equipment: n.a.
[*]Preferred heating technology: currently district heating for heating (high pressure, direct without heat exchanger), hot water instantaneous heater/boiler. Planned: district heating for heating and hot water with buffer storage and connection option for additional alternative energy sources (solar thermal, geothermal [only shallow foundation allowed!]). Air heat pump probably unsuitable due to lack of underfloor heating, possibly possible after renovation in bathroom/kitchen.

Floor plans (original condition, without conservatory):
Order: basement, ground floor, upper floor, cross section

Exterior views:


3D drawing with comparison original (with old terrace) and conservatory extension (including new terrace):

(dark green lawn = building window)

As mentioned at the beginning, we are planning in the mid-term to replace the conservatory with a better solution.
The goal is to have a room that serves a similar function. That means a sunny room with a nice view of the garden, for example through large lift-and-slide doors. However, it should also meet the requirements of a living space (i.e. proper thermal insulation, solid walls instead of aluminum profiles, proper heating, tight roof).

However, we are still unsure about some fundamental issues:

[*]Separate room or large opening to the living room (and possibly partition there – i.e. “rotation of the living room”)
[*]What happens with the bedroom (balcony not necessary, so far no sloped ceiling, will a dead space or a walk-through room be created)
[*]Which roof shape (extend existing, new roof with flatter pitch in front, side wing with its own ridge direction, but no flat roof or cube)

Option 1:

[*]“Separate” extension with its own ridge
[*]Advantage: depth variable according to space requirements, as long as proportions to main house are okay
[*]Disadvantage: bedroom becomes a walk-through room with little light and what purpose does the additional room on the upper floor serve (observe 2m line)?

Option 2:

[*]Own roof with flatter angle
[*]Advantage: size remains variable, light in bedroom (balcony door becomes window)
[*]Disadvantage: appearance and proportions, roof too flat

(Image in next post)

Option 3:

[*]Extension of existing roof,
[*]Advantage: best optical solution, subtle modern elements possible (e.g. large window), thus light in bedroom as balcony door remains as floor-to-ceiling window with a parapet
[*]Disadvantage: bedroom window (formerly balcony door) in room, room depth exactly defined by intersection with roof.

(Image in next post)

Current use:
The bedroom on the upper floor is used exactly for this purpose. That means it does not need to be larger since we spend most of the time elsewhere. A walk-in closet or a laundry temple are also unnecessary.
The bathroom is sufficiently large, after remodeling a shower + bathtub + WC + washbasin will fit there without problems. The extra shower will be removed, that will become a storage room – possibly the WC will be moved from the bathroom to there).
The other room is an office and guest room. It seems that having children will still work out, so it could soon become a children’s room. Guests can easily sleep in the living room and home office work could also be done elsewhere (it is only mobile working as needed and not external sales).
It would of course be interesting what fundamental possibilities an extension offers to get more out of the ground floor. I would rather not move the kitchen, it currently has brand new electrical, water and sewage lines and just needs renovating and new furnishing. The size is sufficient and we gladly forego an open kitchen.

There might also be a completely different or complementary option:
According to the development plan, this plot is the only one where the garage area is included in the building window. That means apparently residential construction is also allowed here. However, the corner is somewhat shady due to neighboring buildings, so the ground floor would hardly be suitable for residential use (but maybe garage with office/guest room upstairs).

Which option would you prefer most, or am I not seeing the forest for the trees?
What might such an extension (fully basement!) roughly cost?

Thanks in advance to everyone and I am happy to answer any questions.

Addendum: Pictures of the other variants (due to image limits)

Variante 2:



Variante 3:

According to the development plan, the property is the only one where the garage area is included in the building envelope. That means residential construction is apparently also allowed here.

I don't really see living space without a boundary distance here; after all, it is not a semi-detached house. So far, nothing comes to mind, so after the first reading I will initially just say: Thank you for the interesting project and the clear presentation of the basics.

(dark green lawn = building envelope)

... it would be even better with color differences showing where the "extension" or "changes" begin.

I want to revive this thread and submit the colored pictures.

First the existing situation: Here the winter garden and the balcony slab of the upper floor as well as the current terrace are marked in yellow. None of this is in good condition, it darkens the living room and should therefore be replaced.


The idea is to build a fully basement extension at the same location. The question is whether it should be one or two stories and in which design.

The first option would be a "normal" extension, which requires a bigger intervention in the roof:


The second option is only one story, but with more room height. For this, the balcony door on the upper floor becomes a window:


The third option is a continuation of the roof surface and a gallery window from the bedroom into the new room.


The second and third options are limited in size, as they depend on other existing objects (roof, window). The first option offers the most flexibility. Below are a few floor plan ideas for the 1st option.
Since there is now a child on the way, the previous guest and study room will be lost. At least for the home office, there will initially be a solution in the storage room on the upper floor west. In the long term, however, a guest and study room would be better again, especially also as a reserve in case a second child should come.

The idea would be to enlarge the living room on the ground floor by the extension. Currently, the western area is the living corner and the dining area is on the east side. By enlarging the door to the current winter garden, the eastern side could benefit from more light. However, I am unsure about the design and arrangement of the furniture. Even now it was not easy to position the couch sensibly in relation to the TV.

Alternatively, the opening could be even larger and an independent room could be created on the east side, and the western area could be separated by a wall at the level of the beam.


On the upper floor, the question arises about the long-term use. If the new room were only attached to the current bedroom, it would become a passage room. This would make use by guests or a child impossible. Therefore, the idea is to separate part as a hallway. The question is whether this can be implemented sensibly with the ceiling height due to the roof pitch on the side of the extension.


Nothing unusual happens in the basement. For accessibility of the drainage (which must be renewed anyway and is currently inaccessible under the winter garden), we are planning the extension with a basement as well.


Are there any suggestions and criticism of the first ideas? Alternatively, instead of an extension to the south, an extension to the east side is also possible. The building window is visible in the 3D views as a different shade of green. Where can I get the exact measurements? In the development plan from the 60s it is only roughly recognizable.

As a supplement:
The previous owners had also planned an extension. However, a few dimensions larger and with extensive remodeling of the existing structure. I found the approved plan in the building file, but in the end, they preferred to build completely new:

Option 2 appeals to me least visually. Approval feasibility clarified?