ᐅ Improvement Suggestions for a Single-Family Home with 137 sqm of Living Area and a Secondary Apartment

Hello, we are planning our house, which we want to share with my mother (separate apartment approximately 70 sqm (750 sq ft)). We want to maximize the floor area with 137 sqm (1,475 sq ft). Maybe someone has ideas, suggestions, or improvements. We are grateful for any input.

Development Plan / Restrictions
Plot size 459 sqm (4,940 sq ft), 21.5 * 21.4 meters (71 * 70 ft)
Site coverage ratio 0.3
Building area 15.4 * 13.4 meters (50 * 44 ft)
Building line 3 meters (10 ft) and boundary line 5 meters (16 ft)
1.5 storeys
Roof type: steep roof, minimum 35 degrees
Street-facing gable
Maximum heights / limits 9 meters (30 ft)
Other requirements: max 1.15 meter (3.8 ft) knee wall

Owners’ Requirements

2 storeys + expandable attic
Upstairs: 5 people, including three small children. Ground floor: 1 person, mother
Space requirements ground floor
Mother’s apartment: 2 rooms + living room + open kitchen,
separate office with WC.

Space requirements upstairs: 3 children’s rooms, master bedroom, open living and kitchen area, two bathrooms

Office: home office, possibly for visitors

Conservative construction
36 cm (14 inch) masonry
Open kitchen, kitchen island upstairs
Number of dining seats upstairs 6-8
Possibly a balcony
Garage added later
Staircase to attic with roof window accessible from both households

House Design
Designed by:
- Do-it-yourself
What do you dislike? Why? Dark corridor
Personal budget for house including fittings: 400,000
Preferred heating system: heat pump

Why is the design like it is now?
What do you think is particularly good or bad about it? Maximum size utilized, difficult implementation due to sloping roofs

Thank you, maartina