ᐅ Multi-generational house with an underground garage for three families

If I understand correctly, the plan is for a three-family house consisting of two family apartments and one granny flat. It is also supposed to have an underground garage. A 1000 sqm (approximately 0.25 acres) plot is borderline: the flatter it is, the easier it will be to build a house of this size on it; however, an underground garage also requires an access ramp. The longer the ramp must be (because the plot does not help to overcome the height difference), the more space it consumes (taking away parking spaces, which is the reason for building the garage in the first place). An underground garage with six parking spaces is a spatial Pyrrhic victory. Double parking systems would be more economical in that case. By the way, managing two tenants for roughly half an apartment each is hardly worthwhile either.

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And, slope? Is the site plan correctly oriented to true north? (Unfortunately, this question needs to be asked frequently here because it often isn’t the case and the north arrow is missing.)

What about number 8… houses, sheds?

2x200m² (2,153 sq ft) and a granny flat… how large? If it’s for parents, what are the requirements?

Long building structure, with each main unit being 10 meters (33 feet) in length, separated by another 10 meters (33 feet) length for the accessible in-law apartment for the parents. The total width is a maximum of 11 meters (36 feet), which allows for a 3-meter (10 feet) deep terrace on the south side within the boundary setbacks to the north and south. This leaves 20 meters (66 feet) of garden or driveway space, divided between the west and east sides. On the west side, the driveway to an underground garage shifts the equivalent garden use for the two main units slightly to the east. Approximately 8 meters by 20 meters (160 sq m / 1,722 sq ft) of garden remain on the east side, and on the west side, due to the driveway, access to the underground garage, and entrances, about 12 by 12 meters (144 sq m / 1,550 sq ft) of garden space is left. In addition, there are the access areas (each 10 by 3 meters / 33 by 10 feet) and the terrace sides (each 6 by 10 meters / 20 by 33 feet), where each has a 3-meter (10 feet) deep terrace.

The upper floor (including the area above the in-law apartment) can be shared between the main units.

If you then subtract a strip of hedge about 1 meter (3 feet) wide all around, not much space remains.

This might be enough for some, but not for others.

11ant schrieb:
If I understand correctly, it’s planned as a three-family house consisting of two family apartments and one granny flat. And there will be an underground parking garage. The 1000 sqm (10,764 sq ft) plot is borderline: the flatter it is, the better a house of this size can be built on it;

Hello 11ant. First of all, thank you very much for your explanations. Yes, your definition hits the mark very well. We are fully aware that 1000 sqm (10,764 sq ft) is borderline, especially if you want to keep some garden space. Nonetheless, I think the conditions are met. The plot is completely flat with no slope at all.

11ant schrieb:
An underground garage with six parking spaces is a Pyrrhic victory in terms of space.

If it works out that way, I would also call it a Pyrrhic victory!

11ant schrieb:
By the way: playing landlord with two parties roughly half a residential unit each is not really worthwhile either.

Currently, there is no plan to rent out the granny flat. Later on, it will also not be used for rental purposes. The idea of stacker parking systems is definitely worth considering. Personally, I find it a pity that quite a bit of space would be lost or could be lost here. Do you perhaps have a visual suggestion for this?

kbt09 schrieb:
And the slope? Is the site plan really oriented to north? (Unfortunately, this always needs to be asked here because it’s often not the case and the north arrow is missing).

Hello kbt09. Thank you as well for your questions. The site plan is oriented to true north. There is no slope. The plot is completely flat. Number 8 consists of a single-family house (2 full floors / finished attic / hip roof). At the property boundary there is also a large former garage used as a workshop.

kbt09 schrieb:
2x 200 sqm and granny flat… how big? If for parents, what are the criteria?

Two times 200 sqm (2,153 sq ft) would probably be the maximum and, in our opinion, quite feasible. For the granny flat, 60 to 70 sqm (645 to 753 sq ft) would be absolutely sufficient. Accessibility is of course important, although this could also be solved with an elevator. Otherwise, there are no major requirements for the granny flat, as it will only serve as a “base” for the parents, who are typically away around 6 to 7 months a year (as long as health allows).

Thank you very much and best regards.

ypg schrieb:
Longer building structure, with each main unit being 10 meters (33 feet) in length, and in between, also for accessibility reasons, a 10-meter (33 feet) long granny flat for the parents. The total width is a maximum of 11 meters (36 feet), which still allows for a 3-meter (10 feet) deep terrace on the south side respecting the boundary distances on the north and south sides. This leaves 20 meters (66 feet) of garden or driveway space, divided between the west and east sides. On the west side, the driveway to an underground garage shifts the equivalent garden use for the two main units somewhat to the east. Approximately 8 meters by 20 meters (160 sqm / 1,722 sq ft) of garden remain on the east side, and on the west side, due to the driveway/access to the underground garage and entrances, there is 12 by 12 meters (144 sqm / 1,550 sq ft) of garden. Additionally, you have the areas for the entrances (each 10 by 3 meters (33 by 10 feet)) as well as the terrace sides (each 6 by 10 meters (20 by 33 feet)), where each unit has a 3-meter (10 feet) deep terrace.

Upstairs (the area above the granny flat can also be shared by the main units).

If you subtract a 1-meter (3 feet) wide strip for hedges all around, not much remains.

This may be enough for some, but not for others.

Hello ypg. Thank you very much for your detailed explanation. I’m trying to visualize it, which is always a bit challenging for me!

Muc1985 schrieb:
Hello ypg. Thank you for your detailed explanations. I’m trying to imagine it visually (which is always a bit difficult for me)!

You just need to picture a building approximately 30 meters long (98 feet), 11 meters wide (36 feet). Visually, it resembles a row of three townhouses.
At the front, there is the driveway plus entrance… and also 144 m² (1,550 sq ft) of garden in the western third, while at the rear there is 160 m² (1,720 sq ft) of garden in the eastern part.
This is the simplest version and already pushes the plot to its limits.

My honest opinion: if you have enough money that this supposedly doesn’t matter here, then I wouldn’t subject myself to a) building in a tight, controlled space with family members (it’s no longer spacious here) and b) basically overdeveloping a plot like this.