Old building renovation some questions

Hello everyone.

I am planning to renovate my house.

It looks like this:
Back in 2001, we attached an extension to my parents' house (to which my 10-year-old sister had already added an extension).
So it is a 3-family house. My sister and her husband live on the 1st floor, and we live on the ground floor, which is divided into 2 apartments of about 85m² each.
On the ground floor lived my parents (unfortunately both already deceased) and my family and I (each in completely separate apartments).

Parents' construction 1972
Sister's construction 1991
Mine 2001

Now we are considering converting these two apartments into 1 large apartment.
For this, we would have to make a few openings 2-3 (we are not quite sure yet how the corridor should look) in load-bearing walls (which means installing beams).

So, here is what we plan to do:

First and foremost, everything should be barrier-free. Living space would be about 160m².

I would keep the living space layout of the parents as it is because everything is already very well divided; the only thing to do there would probably be to tear down a wall (most likely not load-bearing) between the kitchen and dining room because we want that to be open and to move and enlarge various doors.

The exterior is already insulated (that was all done with our extension), so no need there.

Our rooms would only be slightly reduced in size by the corridor we are planning.
This would be done with drywall and good sound insulation.

In addition, we would tear out all floors (partly tiles, partly laminate), and then the screed would have to be leveled (the differences are not big, but still there).

Now about the bigger projects:
HEATING: GAS
We currently heat the entire house with oil; the burner and tank are located in my sister’s basement part, but since we plan to be completely separated (we get along very well, but if we are already tearing down walls, then thoroughly), we would need a new heating system.
We would switch to gas because the neighbor already has a gas line that we can connect to.

FRONT DOOR:
Currently, my sister and we use the same entrance, which will change when we merge my two apartments.

ELECTRICITY:
Possibly completely rewiring. It’s relatively okay especially in our area that was built in 2001, but I would like to install LAN connections everywhere and more power outlets.

CEILINGS:
New drywall ceilings throughout the apartment (I would also run all cables above that unless you say that would not be a good idea).

DOORS AND FLOORS:
About 12 doors and new floors for the 160m².

BATHROOM:
One completely new bathroom (the room exists, but with new tiles, fixtures, shower, etc.)
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I had a drywaller (a friend) with me over the weekend who has renovated many houses and then sold them again.
I know his work and am more than satisfied with it.
I told him about my project (he would also look after the various people like plumbers, electricians, tilers), and he estimated my project at about 70-80 thousand euros. However, he advised planning for 100,000 just to be safe, because, in his experience, unexpected things can always come up.

Do you think these figures are realistic?

So, briefly summarizing the work:
New heating, possibly complete new wiring, new drywall ceilings, new doors and floors, new bathroom.

NO windows, no roof (completely rebuilt in 1991, newly roofed in 2006), no insulation (already there).

I would do the chipping myself, also afterwards the flooring and painting work (only tiling I cannot do).

What do you think? I know it’s of course hard to say without plans etc., but a rough estimate would be interesting.

Best regards

I would say that is roughly correct. The structural work is missing from your list. Entrance door / windows remain?

Hello!

What do you mean exactly by the shell construction works?

Insulation is already in place everywhere, the only thing to be done on the outside or on the exterior wall is to install a new front door, otherwise windows and wall will remain untouched.

Best regards

Oh yes, and possibly a chimney pipe still needs to be installed, which will be routed up along the house wall for the gas heating, and the roof must be slightly opened in the [zug] for this pipe (that’s what the chimney sweep said). Because the exhaust gases must clear above the roof surface.... At least that's how I understood it.

You first need a structural engineer to take care of the issue with the openings. Load-bearing walls are not to be taken lightly. He will also quickly be able to tell you what is feasible and what is not.

Break down the work according to trades and assign prices.

The breakthroughs and the interception is what I meant. A chimney also costs a lot of money. Still, with 100k you are not badly positioned at first. You don’t seem to be completely clueless either and can do a bit yourself, that already helps if you don’t have to call someone in for every little thing.