Build, buy, renovate? - How reasonable is it when desiring a modern house?

By a "normal cost approach" I understand that if I have a purchase price of €350k, I don't have to invest another €250k.
A contemporary insulation, windows, heating, and photovoltaics would be especially important to me.

The costs primarily depend on two factors: the standard land value or location, i.e. the purchase price. What do you get for €350,000 with you?
The second essential parameter is living space. €250k renovation on 150m² living space is €1666 per m². That is cheaper than a new build for €2500/m² (plus incidental construction costs).
As a very first rule of thumb: as long as the purchase price minus standard land value plus renovation costs stay below these €2500/m², in my opinion it is okay.

Now you of course already have wishes that drive up prices: photovoltaics, insulation, presumably underfloor heating.

@Tassimat: What measures did you have to take and what was the biggest challenge?

Everything, including new interior plaster, because it was a smoker's den. I also wanted photovoltaics once, but then that was cut due to the costs. Also, there was no free roof space.

The biggest challenge was probably the stress of managing everything on time: work, children, planning, own effort, constantly coordinating craftsmen, being on the construction site every day... and that for more than a year. But I was motivated, and that is essential.

We have completed a full renovation of a house built in 1958. First of all, I would like to state that the 2 years were a very intense period, which is why I would never do it again. Despite everything, we do not regret it. Although we contributed a large share of the work ourselves (complete gutting, construction of the desired shell, drywall, electrical work, site management & structural engineering, etc.), we ultimately ended up almost at the cost of a very cheap new build, with the structure being very good and no surprises. Thus, we clearly exceeded the often quoted 500-1000€ per m2. Also, the region is certainly rather cheap in comparison. Renovating an old building is time-consuming and in terms of costs sometimes even more expensive than new construction (for example, plaster thickness in old buildings). However, with money, almost everything can be changed. For example, we eliminated 6 walls and converted the basement into a living basement. In addition, we placed value on achieving today's standards (underfloor heating over 3 floors, wall heating in the basement, insulation, network, barrier-free showers, etc.). In hindsight, an old building is certainly better suited for builders who are not prone to always chasing the latest trends and who continue to use the existing "substance." The advantages for us are the large plot in the established old building environment, the possibility for own work, and the charm of the house. On the downside, you always have to live with certain compromises despite everything (e.g., ceiling height). Also, reaching the energy consumption of a Kfw 40+ house will be difficult. We learned a lot and would certainly do many things differently now. Hopefully, we never have to do it again :).

At some point, you have to make a decision. If you have two left hands and don't dare to do anything, you should reconsider renovation or invest a lot of money in craftsmen. I find bringing a house up to date suspicious.

1. Assuming we buy a house from the 70s and bring it up to the latest state of technology, that doesn’t change the year it was built. What disadvantages arise from this regarding durability, etc.?

With proper substance: no disadvantages – just to reinforce the statements of previous posters.

2. Who of you has experience with such a project and would be willing to share it here? Was it worth it? Would you do it again? What are, from your point of view, the advantages and disadvantages?

Second-hand experience, a friend’s project with renovation of an old building and new extension: It was totally worth it, resulting in a characterful ensemble. Our friends had an extremely tight budget and did a lot of the work themselves. I wouldn’t have had the perseverance to work and live daily and on weekends at the construction site for months as a large family. For our friends it was hard but right; for us it would have been overwhelming. Advantage/disadvantage assessment: When modernizing something existing, it’s easier to develop an idea of how it will be to live in the property. With a new build, there is the chance to be structurally creative if you want. Both ways can lead to a wonderful residential property.

3. We value energy efficiency and modern heating technology (preferably air/air or air/water including photovoltaic system). Is something like this possible within the scope of a renovation and a normal cost framework?

Achieving energy efficiency in an older building is not quite as easy as with a new building, where the wall construction is designed for this efficiency from the outset. Extracting the “last efficiency percentages” will be expensive. However, when considering the overall picture, renovating an existing building has the edge when it comes to climate neutrality, because a lot of energy for construction effort is already stored in the building and does not have to be newly invested. So if efficiency is primarily important to you because of climate protection, then you are very likely better off buying an existing property.

Hello, thank you very much for the numerous responses. I was unfortunately massively busy with work this week, so I am only replying now.

The already existing floor plan would be more of an advantage for us, as it would save us the creative part (for which I would be very grateful ;-) ).

As far as our manual skills are concerned: I think the limiting factor for us is the lack of experience on construction sites, which means for me: We could do something, but in some areas we are not quite sure what we are doing. Ergo, only simple work.

The modern energy standards are important to us for two reasons. The first reason is sustainability in general, whereby the aspect that the construction work does not have to be done anew when buying is a new but interesting thought for me. Otherwise, we want to make ourselves as independent as possible from energy prices for economic reasons, and to be honest, when it comes to technology, I am still quite the playchild.

Regarding the standard land values, I have found that these only apply to price determination to a limited extent. There are houses from the 70s on 700 sqm plots, partially renovated, for €440k. Overall, however, a lot of money for many compromises we would have to make.

We are generally considering a budget increase, the banks would give us significantly more money and we could manage the whole thing, but I am not really willing to spend €650k or more on a house.

The good thing is that we basically have no time pressure.

In mid-September, decisions will be made in the new development area around the corner about how many plots will be returned from the reservations.

Is there anyone here who has switched from an oil/gas heating system to modern heating technology? I would be interested in what work is involved.

Best regards and have a nice weekend!

In mid-September, decisions will be made in the new development area around the corner about how many plots will be returned from the reservations.

Oh dear, will no one move up then - or did you mean becoming a substitute yourself?