ᐅ New construction, 200 sqm plus basement, with a mansard roof

Hello everyone,

after a long time of reading and several planning rounds, we would like to get your opinions on our current planning status.
The plot just outside Hamburg is already secured but is very long and narrow (widest point 20m (65 feet)).
There is no local development plan, only a building envelope diagonally crossing the plot with a width of 20m (65 feet).
Due to the relatively high groundwater level from the marshy soil, the basement can only be dug about 1.5m (5 feet) deep, possibly only 1m (3 feet). This will be clarified this week when the soil report arrives.
At the start of our planning, we intended to have 1 office and 2 children's rooms; however, due to changes in our professional and personal circumstances, we now need to plan for 2 offices and actually 4 children's rooms...

Building Regulations / Restrictions
Plot size: approx. 1000m² (11,000 sq ft), width 16-20m (52-65 feet)
Slope: gently sloping, approx. 1m (3 feet)
Floor area ratio (FAR) / site coverage: no specification
Building envelope, building line, and boundary: yes, building envelope diagonally across the plot, 20m (65 feet) wide, otherwise usual 3m (10 feet) setback
Number of parking spaces: 2 (1.5 per housing unit)
Building height: max. 12m (39 feet)
Roof shape: no specification
Architectural style: no specification

Homeowners’ Requirements
Style, building type: classic, townhouse
Roof type: mansard roof (very typical for this area)
Basement, floors: basement + ground floor + upper floor
Number of occupants, ages: 6 (two adults, 2 children + twins coming soon 😀)
Spaces on ground floor: living room, separate kitchen, 2 offices (both working from home, one also serving as a guest room), guest toilet, sufficient storage space is essential for 6 people
Spaces on upper floor: master bedroom, dressing room, master bath, children’s bathroom, minimum 3 children's bedrooms each at least 15m² (160 sq ft)
Offices: 2 due to parallel home office use
Number of guest stays per year: about once a month
Open or closed floor plan: closed
Conservative or modern construction: conservative / classic
Open kitchen, cooking island: closed kitchen without an island, but a freestanding side-by-side refrigerator would be great
Number of dining seats: 8-10
Fireplace: yes
Music/sound wall: no
Balcony, roof terrace: yes
Garage, carport: yes, double carport
Utility garden, greenhouse: no
Additional wishes / special features:
- Master bedroom may only face the garden
- Possibility to add a granny flat in the basement later
Style, roof form, building type: townhouse style with mansard roof. We like the mansard roof because it limits roof slope restrictions on the upper floor and visually reduces the height somewhat. Due to the basement partially above ground level, the house otherwise appears quite tall for 2.5 full stories.
Basement, floors: basement, ground floor, upper floor

House Design
Who designed the plan: custom design by the architect of the planned general contractor
Offer for the house (including painting, flooring, and pre-selection): approx. 850,000 EUR

What do you particularly like? Why?
The ground floor overall is good, open staircase to the hallway, double doors to the living room, kitchen can be opened to the living room by sliding door, we like the mansard roof as well.
Children's rooms are all about the same size.
Laundry chute.

What do you dislike? Why?
- The house is quite large, but some rooms still feel tight, especially upstairs
- Master bathroom is too small; we would like a 1.8m (6 feet) bathtub, washbasin with two sinks, and a 1.4m x 1m (4.6 feet x 3.3 feet) shower. A separate toilet is "nice to have" but could be integrated into the bathroom if that solves the problem.
- Dressing room is borderline narrow, but the bedroom cannot be significantly reduced.
- We would actually need another children's room. The idea now is that the younger children share a room at first until eventually one office from the ground floor moves to the basement... or a child 😉
- Kitchen on the ground floor is a bit too narrow; we won’t be able to fit the freestanding side-by-side fridge.
- Window in the office /
- Windows on the east side (street side) are unfortunately not very symmetrical from the outside.
- You have to walk around the house to reach the carport; no direct access from the basement to the carport or garden. However, if the carport were on the north side, the house would shift too far to the south side. There is a large/tall 5-family house about 3m (10 feet) away on that side, so more setback there means more sun exposure.

Preferred heating technology: ground-source heat pump

If you had to give up something, which details or additions?
- Can give up: actually nothing 🙄 maybe the fireplace.
- Cannot give up: basement, laundry chute, min. 15m² (160 sq ft) in the children's rooms, children's bathroom, shower in guest WC

Why is the design the way it is?
Two years of planning have gone into this 😀
Started with our own sketches, then last year the first attempt with an architect whose designs we didn’t like, so we didn’t find common ground.
The plan from the architect of our preferred general contractor hit the mark much better on the second attempt.
We are basically quite satisfied; most of our ideas could be incorporated except the points mentioned above.

What is the most important/basic question about the floor plan in 130 characters?
How to get more space for the master bathroom upstairs? We just can’t find a solution without extending the whole house by about 20cm (8 inches).
Where else do you see room for optimization?