Single-family house approx. 155 sqm + separate living unit 40 sqm. First draft. Any suggestions for improvement?

I expand on ’s advice: build it like this, without a granny flat and without a second door to the bathroom.

Seriously, why the apartment? Do you pay 1000 euros cold rent in your area or why would you voluntarily bring strangers into the house unnecessarily? Above all: the rental income is offset by the additional costs of implementing this granny flat. So you can also just leave it out.

Then I finally question the budget. At least the lower limit of the mentioned huge range. 155*2000 (where is the construction site?) = 310k. If the basement is to be implemented like this, you can basically calculate it similarly: 40*2000 = 80k. Plus about 30k for the garage. That makes about 420,000 euros plus additional costs... so 470k. Then there is something about KNX and so on.... I think a 5 definitely comes before that...

Then I will finally question the budget. At least the lower limit of the huge range mentioned. 155*2000 (where is the construction site?) = 310k. If the basement is to be implemented like that, you can actually calculate similarly: 40*2000 = 80k. Plus about 30k garage. Makes about 420,000 euros plus additional costs... so 470k. Then there is something about KNX and so on... I think a 5 is definitely ahead of that...

The 155 is already nonsense. The floor has about 92 sqm. Three of those = 276 x 2000,-€ = 552K just for the house. Plus garage including roof garden estimated at 60K (it is big and the terrace huge) + earthworks for the house, basement sealing, lines and stuff 60K if lucky. 30K buffer = 700K minimum.

What cost range would you set here for additional construction costs? ... without costs for outdoor facilities and interior fittings.

real: 750K

Costs with a lot of own work (also electrical, sanitary, tiles since acquaintances from the specialist areas will come and help)

700K

I think architects should be held liable for the numbers they state. The 350K is an outrage towards the client.

Aside from that, how much time do your acquaintances have? I wouldn’t expect too much. Do they all want to sacrifice their annual vacation for your house for free? I can’t imagine that.

Overall, the floor plan in the main apartment definitely works, but there are a few things I would personally change.

A storage room is missing on the upper floor. The children's bathroom could be made a bit smaller and some space could be taken from the gallery. Or make the master bathroom downstairs smaller earlier, without access from the gallery, and instead have a little room there.

Sliding door between bedroom and dressing room

The wall between the two children's rooms with alternating niches for built-in wardrobes (or in the Ikea-Pax grid) like in US houses: super practical, creates a calmer front

Hi Matthew, in this location, according to several rent index sources and realtor information, it would be about €11-12/sqm, so approximately €400 cold rental income + possibly a carport space and a yield of around 5%. During my studies, we even lived with 3 students in a basement flat shared apartment (3 rooms, 1 bathroom, 1 kitchen) with a family owning a single-family house. Due to a separate entrance to the basement flat and the main living area, the contact with the landlord (despite 2 children) was hardly noticeable for any of us.

Regarding the floor plan: I also find the entrance to the granny flat questionable, especially since every time you leave the house you risk being hit by a car.
Upper floor suggestion: make the walk-in closet wider, remove the second door to the bathroom:

Rearrange the bathroom! In my opinion, it’s a disaster.

In this place, according to several rent index sources and real estate agent information, it would be about 11-12€/sqm, so about 400€ cold rent + possibly a carport space and a yield of about 5%.

You have 47 m2 in the granny flat (not 40 m2. And the main apartment well 180 instead of 155 m2 BTW...). So 500 euros.

You had specified the 155 m2 and the architect then gave you the plan with 180 m2 without comment? Hopefully he can calculate the construction costs better than the sqm that are actually simple to determine.