ᐅ Single-family house design with garage/carport – request for feedback

Hello,

I have been following the forum for a while and now want to become active myself. My wife (29) and I (32) have reserved a plot of land for which we have created a first draft to check if our ideas are feasible on this site. We have already gone into great detail, so by now there is an almost finished plan. I would like to present this today and ask for your evaluation/critique. Please feel free to be brutally honest ;-)

First, the list of questions:
Development plan/restrictions: Everything except flat roofs is allowed, max. building height 9.0m (30 feet), two stories, site coverage ratio 0.4, floor area ratio 0.6, 2 parking spaces, no requirement for ridge direction, border development with garage possible, building permit inquiry has already been submitted and approved positively.
Plot size: 830m² (8,930 sq ft), completely flat

Owners’ requirements:
Style, roof type, building type: somewhat modern look, gable roof (15°), single-family house with office (permanent home office)
Basement, floors: usable basement under main building, 2 full floors
Number of people, age: currently 2 people, 29 and 32 years old, two more planned :-)
Space requirements on ground and upper floor: approx. 160-180 m² (1,720-1,940 sq ft)
Office: home office
Overnight guests per year: about 5
Open or closed architecture: open style
Conservative or modern construction:
Open kitchen, kitchen island: open kitchen
Number of dining seats: permanently four, option to expand to 10-12
Balcony, roof terrace: no balcony, possibly the flat roof annex could be used as a roof terrace
Garage, carport: double garage

House design:
Who created the plan: self-drawn; the basic requirements were discussed with a friend who is an architect (though she does not have much experience with single-family houses yet!)
What do you like most? Exterior views, bright office with garden view
What do you dislike? Rooms on the upper floor are somewhat oversized
Cost estimate according to architect/planner: –
Personal budget limit for house including features: €330,000
Preferred heating system: wood pellets (condensing technology), underfloor heating

I hope the design is clear in all aspects. I am a mechanical engineer and created the entire design with SolidWorks, which is certainly not the standard software for this purpose. But in return, you get everything in 3D and nicely colored :-)

The main problem I currently see with the design is that because a certain amount of space program is assigned to the ground floor, the footprint becomes so large that the upper floor and basement end up hopelessly oversized. Perhaps the overall length could be slightly reduced by enlarging the annex (the guest room would then shift further into the office cube). But maybe a completely new arrangement would also be sensible.

A quick note on our life situation: I work for a small engineering office where everyone works full-time from home for flexibility reasons. Therefore, the boundary between living and working sometimes blurs for me. So I need a room where I am sufficiently secluded to have peace and quiet, but still close enough to participate in family life.
We want to have two children, but they should only be born after the homebuilding project is completed. The planned construction start is mid-2016.

If anything is unclear or if information is missing, please just ask. I look forward to criticism and hopefully a pleasant discussion. When you create the design yourself, there are certainly things you don’t notice because you can’t see the forest for the trees.