KFW 153, second residential unit

Hello everyone,

Although this has been discussed in several threads and the original posters were partly torn apart, I still haven’t quite figured it out.

When is it legally permissible to apply for a second subsidy?

We are planning:
Basement living area, 2 rooms + bathroom, approx. 45m². The rest of the basement is utility cellar.

The two rooms together have about 12.5m² of window area. There is a separate entrance, a full bathroom, and a water connection for a kitchenette.

The granny flat is separated from the rest of the basement by a normal room door.

However, renting it out is not planned. At least, we are unsure.
We are considering two options:
1. To rent out the granny flat for a few years until the kids arrive and the children’s rooms upstairs are needed. Then the two rooms in the basement become offices.

2. To use the rooms in the basement directly as offices and only rent out the granny flat when the children eventually move out.

The additional cost for KFE55 would be around €5,000. So it wouldn’t really be worth it with one subsidy. But with two subsidies it would. Then there would be €10,000 repayment bonus + 2x €100k loan...

However, some posts here have made me uncertain whether this would even be allowed...

This is how the KfW sees it. The second residential unit MUST be listed in the building application. However, the normal room door to the rest of the cellar and thus to the rest of the house can be questionable. Unfortunately, I am too far removed from this area. It can, if necessary, also initially be sealed off with drywall.

What matters is what has been approved and designated by the building authority. It then depends on the terms. A single-family house with a granny flat = two-family house. A single-family house with 2 granny flats = three-family house.

How is your building project titled? If it is a single-family house, then there is only 1x KfW.

And if it becomes a two-family house, additional parking spaces will follow as a consequence.

And a simple room door is not sufficient due to the lack of sound insulation. An apartment entrance door must be installed, and the corridor on the ground floor/upper floor must be designed so that the apartment on the ground floor/upper floor is spatially separated from the access to the basement apartment.

So it really isn't that simple.

The next point is not so simple: the KfW funds up to 100 k€ of the proven costs. For 45 m², that makes a price per sqm of 2000 and that's it. You have to prove that to them. It usually becomes difficult when the rest of the house only has a price of 1500. They are not completely stupid either....

Thank you for the previous answers.



There is a side entrance door from the outside. Completely separate entrance with an outside staircase...



In the building application, it would of course state a two-family house. According to the development plan, two residential units are allowed, so no problem...


So the room door might possibly be an obstacle. But as Nordanney says, that could be fixed with drywall.



Thanks for the information, I was not aware of that yet and it is an important hint