Floor plan design for a single-family house with a granny flat

And one more note: Preparing a chimney is difficult because a chimney must be planned, approved, and built for this purpose. However, this is likely to raise the question with the KfW as to why you need a chimney. This actually excludes funding even in the new editions of the funding programs. Even though the stove construction lobby is currently making a big effort and is practically camping in front of the Federal Minister for Building's office, this will probably not be overturned. And don’t ask me why I also know about this and have a stove still in its original packaging in the garage. Whatever you’re planning, it could lead to many discussions.

Oh, this short correction period is really annoying. Of course, it is not the chimney itself that is subject to subsidy restrictions, but the stove.

A second escape route must always be provided like this

It must always be provided – whether there is a granny flat on the upper floor or then also in other rooms on the upper floor that belong to the main residential unit. But as you already say: building regulations are country-specific… only common sense also clarifies a lot (if, for example, one does not know the building location)

The granny flat is actually intended medium- to long-term for a possibly widowed (in-law) parent or a caregiver. We thought it makes sense to consider something like this directly when building a new house. And if later, due to illness – even if only short-term – it should become necessary, living on one floor would be possible. I find it sensible to already take such considerations into account today. However, a commercial rental is not planned. I will definitely clarify the issue again with the relevant parties and then possibly have adjustments made. If it really is that complicated and disproportionate, then I have probably thought too pragmatically, and the granny flat will be removed, which would of course lead to a complete redesign of the floor plan, in which your comments will then be taken into account. In that sense, thanks again for the suggestions!

I find it useful to already consider such thoughts today.

Opinions differ: either the house is already designed to have bedrooms on the ground floor, or other reasons, whether there is one, two, or three bedrooms on the ground floor, lead older residents of a house on private property to prefer moving into a compact city apartment with a roof terrace without gardening. Sleeping on the ground floor is the least problem in old age. Surrendering the driver's license, cane or walker, or simply pain when moving are reasons why one wants to move closer to the center. What good is a bedroom on the ground floor in old age if, for example, you can no longer get into the bathroom? Even the mentioned mother-in-law will "enjoy" walking through the 1.7 sqm hallway ;)

However, commercial rental is not intended.

Nevertheless, you must comply with the framework conditions of a granny flat if you want the subsidy. What you do without funding is still up to you...

intended in the long term for a possibly widowed (in-law) parent or a caregiver.

And if it should later become necessary due to illness - even if only temporarily - living on one floor would be possible.

The catch lies in the details – or in the bed in this room: mother-in-law or caregiver prevent you from using the bed yourself. What we see here is a guest room. And in this regard, other objections to this design still apply, e.g., 3.88 living room dimension, children's room smaller than guest room, etc.

The granny flat is actually intended medium- to long-term for a possibly widowed (parent-in-law)

I would kill my children/children-in-law if they put me in such a tiny apartment. Because that's all it is.