Garage Partially Basement KF40 Compliant

Hello everyone,

we have acquired a plot of land, the area is a new housing development. The house is supposed to be about 140-160 sqm in size. The house will be built solidly.

We currently have the following idea (I am open and grateful for feedback).

Our plan is to build a granny flat as well, since rental income is never bad, especially when you have to pay off a nearly lifelong loan. Furthermore, we receive more KFW funding, and probably my mother will move in with us in about 10 years.

Our plot of land is 515 sqm, is level and 20.93 meters wide from the street side, so not too big. We want to build without a basement. The granny flat, that’s the plan, is to be built above the garage.

Now the actual question, my idea is to put a basement under the garage, since we need and want a bit more storage space. According to KFW requirements, the granny flat must also meet KfW 40 standard. Is it possible to insulate the granny flat so that KfW 40 is achievable? If yes, do you have an approximate cost estimate?

What do you think of the idea?

Thanks & regards

Aside from the fact that a mini cellar makes no sense at all and the garage then requires completely different conditions with the roof structure (structural engineering), the garage would first have to be moved onto the property because living space is not allowed in the setback area (boundary distance).

Our property is 515 sqm, is flat and 20.93 meters wide from the street side, so not very large.

Where is the house supposed to go then?

A garage has 18 sqm, a double garage 36. I consider 36 sqm for Mom already very borderline. How is access supposed to be achieved?

I assume that if you already think there is a free granny flat, you are not even aware that you are talking about comparable extreme additional costs here. 150 sqm is available for 450,000€.
A 50 sqm granny flat is available for 120,000-150,000€, a sturdy double garage from 30,000€, and a mini cellar costs 35,000€ plus earthworks.

Good morning YPG,

that is why I have turned to you. How would you handle the [Einliegerwohnung]? We would like to include the rent and the additional loan from KFW. We just want more storage space. We also had the idea of building an extra floor. The costs were calculated similarly to what you listed above, we estimated around 550K plus a buffer. I know that a [Einliegerwohnung] is not free. We do a lot ourselves since we have a very large family. One brother-in-law is an electrician, the other [SH].

Thanks in advance for the response.

We would like to take advantage of the rent and the extra loan from KFW.

The rent and the loan usually do not really compensate for the additional costs - with the disadvantage that you always have a stranger in the single-family house.

Is it possible to insulate the granny flat so that KFW 40 can be achieved?

Yes.

If yes, do you have an approximate cost estimate?

Only for the insulation? Or for everything?

We just want more storage space.

Attic unfinished.

Only for the insulation? Or for everything?
For everything

Attic unfinished.
Thanks for that

You're right about the strangers. The long-term plan is to take my mother in.
We initially thought to build the double garage with about 50sqm.

I just saw that the KFW loan has almost doubled.

If we build without KFW funding, we can skip the KfW40, right?
Can you still save something that way?

If we build without KFW funding, we can skip the KF40, right?

Yes, then you "only" build KfW 55 and save the extra costs. The difference in energy consumption is negligible.

Only for the insulation? Or for everything?
For everything

420-480k just for the pure house with 140-160sqm
50k additional construction costs (rough estimate)
50k (+X) for the garage
150k 50sqm granny flat
Total: 670k without driveway, terrace, landscaping
less own work

The point in the long run is to take my mother in.

By then you will have strangers in the house – at best on the garage – and in the afternoon it will look towards your garden like in the Muppet Show when Waldorf and Statler sit together comfortably and watch the goings-on in the garden. Sexy.
Does your mother already know that she has to move in with you in the long run, or does she actually want that (it’s often the children’s idea to justify a granny flat).