Building concept multi-generation house approx. 240m², thank you for feedback

Hello dear home builders,

my fiancée and I would like to introduce you to our building project, which is still in its infancy, and get your opinion on it. So far, the idea exists only on paper. We do not have a plot or anything yet.
We also hope you can help us with one or two questions.

PS: We have to warn you... we are beginners in the field of house construction :). (so far I have only read up on various topics on the internet :))

So let's get started:

Development plan/restrictions
Where to build: Rhein-Pfalz-Kreis
Plot size: approx. 400 m²
Slope: no
Site occupancy index: 0.35-0.4
Floor space index: resulting from site occupancy index 0.7 or 0.8 --> 2 full floors
Building window, building line and boundary: -
Edge development: -
Number of parking spaces: 2
Roof shape: open point see storage room question
Style: modern
Orientation: -
Maximum heights/restrictions: -
Type of construction: solid


Requirements of the builders
Style, roof form, building type: open point see storage room question
Basement, floors: no basement, 2 full floors
Number of people, age: 4 (2 aged 55-60, 2 aged 25-30) (future 5-6 people)
Division of apartments: currently 1st apartment 162m² (114m² ground floor, 47m² upper floor), 2nd apartment 81m² upper floor
Open or closed architecture: open point
Conservative or modern construction: modern
Open kitchen, cooking island: open kitchen see attached floor plan
Number of dining seats: 6-8 people
Balcony, roof terrace: balcony yes
Garage, carport: currently double garage planned

House design
Who designed it: own design (static etc., I can only assess limitedly)
What do you particularly like: the large living area
What do you not like: so far no storage/basement replacement available
Price estimate according to architect/planner: -
Personal price limit for the house, including equipment: €450,000 including land & excluding garden work * (20,000€ buffer not included)
Preferred heating technology: due to Energy Saving Ordinance 2016 --> air-water heat pump (heating and domestic hot water) with exhaust air system or gas (heating) and solar thermal (domestic hot water)

If you have to give up something, on which details/extensions
-can you do without: double garage --> single garage and carport in front of garage

* Electrical installation, painting/wallpapering and tiling work we would do ourselves (thank God we have a family of craftsmen :))

my open questions:
- Currently, I tend to use a Poroton T10 brick with 365 mm thickness. A Poroton T9 brick, also 365 mm thick, has better thermal insulation properties, the same compressive strength properties and costs less than a Poroton T10 brick. Can someone explain the connection? You get a better brick on paper for less money?!?!

- In our current floor plan, we have not yet planned a "basement replacement" (or storage room). My idea was to extend the double garage with an additional room (approx. 10 m²) and use it as storage space. However, I now wonder if it is allowed to build a storage room directly on the plot boundary like the garage? Also, the issue of site occupancy index (if 0.35 with the current floor plan) worries me.
Otherwise, the only thing I can think of as a "basement replacement" is a gable roof, which would be a suboptimal solution. Do you perhaps have any ideas on how to create storage space? (I also have

- Should it be a prefabricated garage, is it possible to partially build on top of it? (currently planned in our floor plan)

- Does it make sense to build the interior walls as drywall if the statics of the house are sufficient? I am thinking about different expansion behavior --> cracking.

Those are all the questions that come to mind right now... but surely more will come :)

Thank you very much in advance for your answers.



Regards,
Kirin2k15

Who always places beds so strangely against the wall? :(
Does the kitchen even work like this? The detailed measurements are missing. Children's room 9 sqm?
To me, it so far seems like an idea - never like a serious plan.
With 240 sqm, you can definitely do better with the multi-generational living - also be aware that you need to place special emphasis on soundproofing!

Although measurements are missing, the first glance shows that this cannot work. Kitchen aisles less than 80 cm wide, beds against the wall, rooms 168 cm wide. Interior bathroom, garage for 2 cars only 500 cm interior width, niche width for the stairs only 68 cm ... no one can walk up there, let alone bring furniture up.

And, a house is planned according to the plot (north-facing, access possibilities, etc.) ... planning without a plot is basically pointless.

With 400 m2 and a floor area ratio of 0.40, it will be very tight with the desired construction method. If a double garage and terrace are added as well.

Under 600 sqm of land, something like that won't work, as TomTom already says.

And always plan for the future or remember to use as few stairs as possible. We all get older and even in young years one can be affected.

We are currently basically also building a "multigenerational house" You are welcome to browse my thread and read about our requirements and wishes.

And welcome to the [HBF].