ᐅ Floor Plan Ideas and Cost Estimate for Renovating a Semi-Detached House from 1939

Hello everyone,

now that it has become clear to us (and was made clear) that a renovation is better than an extension in the garden, I would like to ask for advice again from the collective intelligence here.

The facts:

- An architect has been hired and is already working. So far, we like the plan.
- The semi-detached house mainly dates from 1939. The living room on all levels is an extension from 1981, as are the balcony and the double garage.
- The ground floor is occupied by my mother. We live on the first floor. The attic floor is still rented out. The tenant knows he has to leave. The attic space has already been partially converted. It was insulated with glass wool about 10 years ago. Only the painting is missing. It is intended to become my office.
That means we want to combine the first floor, attic floor, and attic space into one unit.

Current ideas:

First floor:

- The existing staircase will be closed off downwards to the ground floor. For “family reasons,” we want a separate entrance. The staircase upwards will remain, or a new one will be installed (or restored?). It is still the original staircase from 1939.
- The entrance stairs will run along the previous balcony. The stairs will go up from north to south.
- Since we have hardly used the balcony due to its dimensions (7 x 2m (23 x 6.5 feet)), it will be used to enlarge the old children’s room and future dining room with kitchen.
- The kitchen will become a vestibule/coatroom and entrance area.
- The bathroom will remain, as it was completely renovated just 3 years ago and will serve as a guest WC/bathroom.
- The bedroom stays.
- The living room stays but should be brighter. That means even larger windows need to be installed.

Attic floor:

- The kitchen will become a utility room with washing machine and dryer. There will also be a staircase to the attic space/office.
- Since the tenant here smokes and the children’s rooms need to be placed here, we will probably have to renovate the entire core (or?)
- The remaining space will become 3 children’s bedrooms plus a bathroom.

Attic space:

- Will be an office. I would like it to be brighter and have more glass. If financially possible, I would like to have a large window with a nice view towards the city center.

Costs:

- An energy consultant recommended by the architect has already been on site. He estimates the renovation costs at approximately €370,000–400,000 (around $400,000–430,000). That leaves me somewhat speechless. I expected half that. Is it really that expensive?
He says that for subsidies, we would have to renovate the roof completely. Roof estimate: €100,000 (about $108,000). Technical systems: €100,000 (about $108,000). Interior finishing accounts for the rest. With €370,000 (about $400,000), more than 5 hours of personal labor per day is expected (!!). Otherwise, it would be closer to €400,000.
Google never shows me costs this high. Of course, costs are difficult to estimate, but this seems quite a large difference.
I would only have the roof redone if it’s really necessary or beneficial. Our focus is on the interior finishing. The subsidies are currently not high enough to make it really worthwhile to invest so much just for that, right?
We want underfloor heating and a ventilation system installed. But does the technical equipment have to be that expensive? The gas heating installed 16 years ago is still working…

Questions:

- What do you think about the floor plans?
- What do you think about the costs?
- What would you have done and what would you leave out?
Our focus is on a contemporary look (bright) and technology (underfloor heating and ventilation system).