Combine two apartments

Hello everyone,

I would like to introduce you to my project. I am open to ideas, suggestions, and feedback.

The house (1967) has two full floors and an already converted attic. The electrical system and plumbing need renovation. On the 1st floor, we have already started with both while living on this floor. The WC, bathroom, hallway, dining room, and kitchen are already done. The ground floor is rented out, the attic is empty. The roof is poorly insulated and covered with Eternit panels (containing asbestos). The roof is to be newly insulated and covered, with one dormer window facing west, possibly photovoltaic panels. As part of the renovation, we want to combine the 1st floor and the attic.

Here is a floor plan of the 1st floor.


The chimney with an external stainless steel pipe exists today (about 20 years old or so).

The first question is, where should the stairs go? The staircase goes up to the attic, but it has no radiators and is therefore a cold multi-family-house stairwell. If you want to use it for the connection between the 1st floor and attic, you would have to close it off from below and somehow make it warm and somewhat livable. Also, it is located farthest away from the perceived center of the apartment (kitchen/dining/living room).
If the stairs should be inside the apartment as a spiral or straight staircase, you lose living space on both levels, but you do not have to walk far to the stairs and it is automatically “warm.” However, you need a hole in the concrete ceiling, which also requires some overcoming.

In the attic, apart from the central heating chimney, there are no load-bearing walls. The first idea is to install a long dormer window on the west side because the bathroom is located above the bathroom on the 1st floor and is hardly usable due to the sloping roof. Also, the view to the west is nicer and the sun sets there. On the other side, you could accommodate bedrooms and children’s rooms, where the sloping roof would not be as much of a problem.

The ridge of the roof runs along the north-south axis of the house. Since there might be a photovoltaic system installed on the roof, the external chimney pipe still bothers me a bit. The chimney itself is to remain. Since a filter will have to be retrofitted within the next few years, the chimney could also be replaced by a new one in a different position on the 1st floor if this could reduce the shadow cast. I am still undecided about that.

The roof will still need an appointment with a structural engineer because the load capacity is probably only sufficient for the lightweight Eternit panels. The facade is not to be insulated but only painted when the scaffolding for the roof is in place.

Now some might wonder why not do everything at once and move out in the meantime? Well, the opportunity to combine the two floors only arose this year. By then, we had already started renovating one half of the apartment on the 1st floor. Since the roof now also needs to be done, there is maximum flexibility in the design.

Am I overlooking something or do you have any suggestions?
Best regards

Here is a floor plan of the 1st floor.

Well, then add the others as well.

Here is the floor plan of the attic as it currently is. The white areas at the edge are the knee walls. On the right side only partially, because the balcony is underneath.


The ground floor cannot be changed at the moment, but it looks almost exactly like the upper floor.

Well, if this is going to move forward here, a lot of information is missing ... room program, how many people are supposed to live there? Would it maybe be better optionally to combine [EG/OG] and rent out [DG]? Radiators or underfloor heating? Approximate budget? etc.

Wouldn't it possibly be better as an option to combine the ground floor/first floor and rent out the attic?

I see a ground floor as possibly easier to subdivide, but regarding that:

there is a lot of information missing ...

Original plans (from which usually even more details can be inferred) instead of sketches without measurements and wall thicknesses would generally help a lot more according to experience.

Hello everyone,
thanks for the two responses. You are right, it is easier to work with proper plans. Attached is the plan of the ground floor (current), the plan of the upper floor and attic as drawn by the architect.

Why not combine ground floor and upper floor? Simply because the ground floor is currently rented and because one needs a small single-level apartment in old age, not a huge two-story place. As a young family you can also climb stairs. The idea is that we will live on the ground floor when we are older.

How many people should live there?
Ground floor, as said, is not considered. In the new upper floor/attic, 2 adults + 2-3 children should live. We are currently still looking for an apartment for grandma. She currently lives alone in a house. Idea 1: terminate the tenants due to personal use (it would be a pity for the long-standing, trusting tenant relationship), idea 2: grandma moves temporarily to the upper floor after combining, where there is still a bedroom. We would then sleep in the attic. However, the apartments are connected with only one kitchen. Idea 3: we find another apartment in the area.

Radiators or underfloor heating?
Currently underfloor heating in the upper floor bathroom and kitchen/dining room. The rest radiators. Planned: underfloor heating also in the new large living room on the upper floor and everywhere in the attic. Goal: air heat pump. If the goal cannot be achieved, we still have a gas connection. Currently the good oil burner.

Approximate budget: The architect roughly quoted us 150,000 euros. Since the facade also has to be painted and we need a new balcony railing, possibly a new front door, I would say 200,000 euros. It should not be luxurious, but durable and sensible.

Thanks in advance for all considerations. Stay healthy!