Renovation of an inhabited semi-detached house.

Good morning,

I am new here in the forum and have already been browsing diligently here in the forum.

Unfortunately, I have not yet been able to satisfy my actual concern. Therefore, I would now like to gather information in this way and hear your opinions on it.

My girlfriend and I have the opportunity to have the house of my parents transferred to us.

The house is a detached two-story, partly basemented two-family house; it was built in 1945 and was renovated in the early 1990s, including double-glazed plastic windows, Velux roof windows, oil heating, and partially the electrical system.
The house is practically divided in the middle, so each apartment has a ground floor and an upper floor, comparable to a row house you might say.

Now we intend to renovate the house because it is really in need of renovation in places.
For example, the oil heating is only for heating but does not heat the running water; as a result, there are still large old instantaneous water heaters installed everywhere.
In addition, there are old galvanized water pipes installed in the house, as well as partly old aluminum electrical cables.
The roof also needs to be redone.
The ceiling height on the ground floor is also very low at just over two meters.

As mentioned, our intention is to renovate the house. A major problem, however, is that my parents still live there and want to continue living there.

Our idea is to renovate one half of the house while my parents stay in the other, then switch when one half is renovated so that the second half can be renovated.
However, there is also the problem of the low ceiling height.
We would like to add a story, which would of course mean that the wooden beam ceiling separating the ground floor from the upper floor must be removed. The roof needs to be completely renewed as the beams are no longer in the best condition.

A new oil- and gas-independent heating system (whether geothermal or another type, we do not yet know) including underfloor heating should also be installed. This should logically also heat the water.

The electrical system must also be completely redone and brought up to current standards.

The house should be as energy-efficient as possible; accordingly, the insulation probably needs to be overhauled and triple-glazed windows installed.

Unfortunately, we have no idea whether it would be feasible to tear down half the roof along with half the wooden beam ceiling, raise the ceiling height/the walls for the new ceiling to an appropriate level, put on a new wooden beam ceiling plus half a new roof, and then do the same from the beginning when the second half is tackled. (Or does it make more sense to tear off the entire roof and half the wooden beam ceiling and then proceed accordingly with the other work?)
All under the aspect that my parents would always be living in one of the two apartments...

We have not yet spoken with various companies or structural engineers, etc.; we first wanted to inform ourselves and make a rough plan of what we imagine and what should be considered, etc. We are of course very grateful for tips and recommendations.

What do you think, would this be feasible, or do you have better suggestions on how and whether this project could be carried out?

And what would it roughly cost?

Best regards

Tukaram

For a complete renovation, I would estimate €2000 per square meter. Whether this is necessary, I would have professionally checked and planned.

Carrying out the work in the first half and only later in the second half seems pointless to me, as you would have to bring the companies twice and your parents would have to endure the stress, noise, and dirt twice.

Are they already retired? If yes: Send them on a cruise for 3 months. Saves all of you time and nerves and might even be cheaper because the companies only have to come out once. You store the things during that time, moving companies take pictures, pack, store, bring it back, and unpack again.

Alternatively, check where it might be possible to rent a small holiday apartment nearby for the time and accommodate them there.

I consider it pointless to carry out the work in half 1 and only later in half 2, because then you have to call the companies twice and your parents have to endure the stress, noise, and dirt twice.

If it were only about new floors, etc., that would be an option. But I can hardly imagine that it makes sense to first add floors to one half and then to the other.