ᐅ Two full stories, pass-through garage, utility room located under the stairs

We have now had several in-depth discussions since the idea of using the space under the stairs as an extension of the utility room and the idea of a direct passage to the garage have developed. Here are the findings, which are basically close to the design that one construction company now wants to finalize and price:

We have now seen the garage passage into the utility room in two private houses (one belonging to acquaintances), and it seems very practical, so we want that. The staircase is closed and basically asymmetrical. It goes up about 9 steps, then a landing, then another 6 steps. Including the landing, that totals 16 steps, or 17 risers. At the second rise, a step can easily be added or removed as needed.

My thoughts on individual rooms:
- Both children's rooms are rectangular and about 17 sqm (183 sq ft). The closet niche in the left children’s room does not seem like a limitation to me. I consider these two spacious children’s rooms, also suitable for teenagers; both have south and garden-facing windows.
-> Children's rooms: OK or not?
- The bedroom is wide enough, with a sufficiently wide passage at the bottom, east-facing; the walk-in closet has over 7 linear meters (23 feet) of shelving and an interior movement space of 1.20m (4 feet) in width.
-> Bedroom/walk-in closet: OK or not?
- The bathroom size basically results from the leftover space. I don’t like small bathrooms or toilets directly next to the bathtub. We want double sinks. We do not want a separate children’s bathroom.
-> Bathroom possibly too large for some tastes but otherwise OK or not?
- We want an open living/dining/kitchen area arranged at a corner. I have seen 4.07m (13 feet) for the living area live at acquaintances and found it good; 3.60m (12 feet) for the dining area with a 90-100cm (35-39 inch) table should fit well. The kitchen includes 6 linear meters (20 feet) of cabinets plus a large separate fridge and freezer. A sliding door is planned to avoid hitting anyone when opening; generally, both the kitchen and living room doors are planned to be open and only closed when needed. This is also how we do it at home.
-> Living/dining/kitchen: OK or not?
- The hallway is now 1.80m (6 feet) wide. We have seen 2.00m (6.5 feet) (very generous; wasteful?), 1.30m (4 feet) in a semi-detached house (functional, works but not impressive), and 1.40-1.50m (4.5-5 feet) in show homes (neutral impression). The coat niche is planned with hangers perpendicular to the hallway direction for jackets, etc. Possibly, another wardrobe will be added in the utility/transfer room to the garage because it is used frequently. Larger shoe storage will also be in the utility room, but some pairs (for me only one, for my wife a few) can remain in the hallway (e.g., between the WC door and utility room door or between the workroom door and the exterior wall or in the coat niche). The WC is planned with a shower mainly for visual reasons, though it will be used occasionally. At 2.5-3.0 sqm (27-32 sq ft), it’s visually too small for a stay room (even if one only spends a few minutes there). The work area in front of the connection niche is partly a passage area and partly for storing drink crates, which can be moved when needed. Next to this is about 2 linear meters (6.5 feet) of additional cabinetry; opposite are the washing machine and dryer under the stairs. The hot water tank could possibly be placed in the rear corner of the utility room since it normally does not require access. (The landing is at the 10th step; the height under the landing and the height of the hot water tank must be calculated and planned in detail.) Or would another necessary technical device be suitable there? If not, that space can remain unused. Next to the washing machine and dryer, there is at least 1.20m (4 feet) available for other appliances or the mentioned second wardrobe. If necessary, the approx. 2 linear meters (6.5 feet) of cabinets will have to be replaced by essential technical equipment, but there aren’t that many devices after all.
-> Hallway, utility room, WC/shower: OK or not?
- There is also a study room, let’s call it the PC room. It houses the computer, some cabinets, and additional storage primarily for documents.
-> Study room: OK?

Now for the details:

Development plan/restrictions
Plot size: 600 sqm (6460 sq ft)
Slope: 2-7%, mostly leveled by us
Floor area ratio: 0.4 plus 50% allowance
Site coverage ratio: none
Building envelope, building line, boundary: none
Adjacent development: none
Number of parking spaces: 2 required
Number of floors: maximum 2
Roof type: single-pitch or gable roof, 25-40 degrees -> planned: gable roof 25 degrees (25°C - 77°F)
Architectural style: not finalized; possibly modern with light plaster, anthracite-colored roof tiles, and dark-tinted exterior windows
Orientation: south-southwest
Maximum heights/limits: eaves height 6.30m (20.7 feet)
Other requirements: corner plot, play street to the north and east; garage or carport only behind the street-facing building line, i.e., at the current location or directly in the south garden; so only possible at the current location

Client requirements
Style, roof shape, building type: 2 full floors, everything else secondary; if necessary, also 2.25m (7.4 feet) knee-wall and gable roof
Basement/floors: 2 full floors on a slab foundation
Number of occupants, ages: as shown
Space needs on ground and upper floors: as depicted
Office: family use or home office? PC room, filing cabinet
Guest bedrooms per year: no
Open or closed architecture: rather open
Traditional or modern construction: hm? Brick or knee-wall plus external insulation, so I would say modern
Open kitchen, kitchen island: yes, see plan
Number of dining seats: 3 or 4 and flexible
Fireplace: not in a highly insulated new build – no
Music/sound system: surround sound (no priority; no sound in other rooms from the central system; integrated plug-sized radios with Bluetooth receivers and plug-sized speakers planned for kitchen, WC, and bathroom)
Balcony, roof terrace: no
Garage, carport: double garage with storage room at the back for garden tools, bicycles, children's toys, etc.
Utility garden, greenhouse: no
Other wishes/special features/daily routine: no