ᐅ Floor Plan Design for a Single-Family Home with a Secondary Apartment

Dear forum members,

I have been following this forum for some time now and have already gathered a lot of helpful information for our planned house construction. Many thanks for that!

We have now finalized our floor plan, and I would appreciate your expert feedback on our designs.

P.S. Since the location and orientation of the house and garage on the corner plot are quite fixed and conform to the development plan, my main concern is the room dimensions and whether the layout, in your opinion, works well in reality. Of course, I am open to any suggestions and improvements.

Thank you in advance!

Best regards


Development Plan / Restrictions
Plot size: 880 m² (9,470 sq ft)
Slope: 3 meters (10 feet) incline from south to north (see attached survey)
Floor area ratio (FAR): 0.4
Gross floor area ratio (GFAR): 0.8
Building area boundaries, building line, and limits: 3 meters (10 feet)
Edge development: Garage directly adjacent to neighbor’s property, up to 9 meters (30 feet) in length
Number of parking spaces: 2

Client Requirements
No basement, 2 full floors
Number of occupants, age: 4 people (2 adults in their mid-30s, 1 toddler, 1 child planned)
Office: occasional home office (2 days per week)
Overnight guests per year: possibly 4–5 times
Open-concept design
Open kitchen with island
Number of dining seats: 8
KfW standard EH 40 compliant (including granny flat)
Potential preparation for a fireplace (installation not allowed due to KfW requirements)
Garage with storage room and carport (also serves as entrance canopy)

House Design
Designer: Architect
What we like: open living/dining area, utility room on the upper floor, storage room with freezer under the stairs, “mudroom” in the technical room, granny flat, half-landing staircase, carport serving as entrance canopy
What we don’t like: possibly the office
Estimated price according to architect: 500,000 €
Personal budget for the house, including fittings: approx. 550,000 € (plus own work)
Preferred heating system: air-to-water heat pump

If You Had to Give Up Certain Details or Extras
Separate walk-in closet, T-shaped bathroom layout

Why the Design Is the Way It Is
Based on our individual preferences and wishes

I would say that the ground floor (GF) was planned first, and only afterwards did they address the unpopular upper floor (UF)...

The secondary apartment is many things, but not a true separate unit, since it uses the same entrance and is not isolated. If you look closely, you actually share a kitchen and living room due to the open floor plan...
Since there is no guest bathroom on the ground floor without the secondary apartment, I suspect that funding is simply being doubled, and the (apartment) door to the secondary unit remains permanently open? If that’s the case, take another close look at the regulations. You’re not the first to have this idea...

What is the additional corner space in the utility/technical room for (right side of the plan)? Storing drinks in the "pantry" or a freezer?
The "pantry" doesn’t really work as such because of the lack of storage options and shelving.

The utility room layout doesn’t function well. Half of the utility room is currently just circulation space. If the doors were positioned opposite each other, at least on the right side of the room there would be a chance to allocate significant space for technical equipment.

The upper floor is awkwardly laid out and completely contrasts with the spacious, open concept of the living and dining area below. When designing the UF it felt like, "Oops, I still have rooms left—how do I get rid of them?"

The hallway is large but cramped; it has heard of daylight but actually receives very little, especially near the children’s corner.
What is the recess from the bathroom toward the utility room intended for? A built-in cupboard?

The chimney flue in the bedroom is very noticeable. Since you can’t install a fireplace, wood stove, or similar there anyway—because it would be in the middle of a circulation area—I would try to better conceal the flue, meaning without a projecting wall element.
Of course, it would be better to omit the chimney flue entirely if, according to KfW standards, it cannot be used anyway. But I assume the rules will be interpreted creatively here, just like with the "secondary apartment"?

All in all, I like about a quarter of the floor plan (GF right side). It’s hard to believe an architect could have come up with this...
Maybe it was a “designer” from a general contractor (GC) who simply put your wishes on paper one-to-one without giving it much thought?

I honestly can’t make the ground floor level work with the slope. It doesn’t add up—there’s about a 1.5-meter (5 feet) difference? -0.25 / -1.75

What are those empty niches in the ground floor utility room and the bathroom upstairs? Also, the wall thicknesses... sorry, this wasn’t planned by a professional architect. Doesn’t a separate apartment need to be at least 26 square meters (280 square feet)?

I feel like I’m being deceived!

Where should the terrace be located? Certainly somewhere near the kitchen, which is also the area where most of the land will need to be filled. How should the slope stabilization be designed, and what does the building permit / planning permission say about this topic?

Personally, I would discard the draft in the Round Folder and start anew with a good architect.

The so-called granny flat isn’t really one. What is it actually used for? You need to provide parking spaces for the granny flat.

How will the outdoor area be designed, including the terrace?
I see the budget as tight, considering all the earthworks, retaining walls, etc.

This is not a granny flat; it is a guest room with a private bathroom.
A granny flat must have a floor area of at least 23 sq m (248 sq ft) and allow for independent household management.