Estimating construction costs. Empirical values

Hello Bauforum community,

my wife and I want to tear down an old barn and build a new building of about 10x10m attached to the existing residential house instead.
We are currently obtaining quotes, but I also wanted to ask here what you think about it. We are calculating total costs of about 120,000 euros.

About 10 years ago, we tore down a large barn and paid about 4000 euros for it. I calculate demolition costs of about 7000 euros since the demolition of the attached barn is more complicated.

The roof of the old residential house, to which the barn is currently still attached, would then have to be closed off. For this, probably 3-4 beams would have to be installed and covered. Insulation is not necessary here. We have no experience with this at all. So x euros, maybe about 4000 euros?

The house itself is a solid construction, 2 full floors with a single-slope roof. Ground floor area 10x10m. The ground floor is not to be developed. So it remains a shell inside. We want to do the interior finishing on the 1st floor ourselves (walls in drywall or solid gypsum). Prepare the electrical work, install radiators, chases, etc.

So we only want to have done:

- Exterior walls, single-slope roof (covered with metal), windows (about 6 simple windows for the ground floor, about 8 somewhat better windows for the upper floor), exterior plaster, screed, heating pipes.

Is it likely to be possible with 100,000?

I see it differently. My first question referred to equity, my second question to the rough cost estimate. I often only know such snappy answers from users in other forums. Since this seems to be part of the daily business here even for the moderators, I am probably not in the right place here. I wish for my account to be deleted. Where do I have to turn to?

I see it differently. My first question referred to equity, my second question to the rough cost estimate. I often know such snappy answers from other forums only from users. Since it seems to be part of the daily business here even among the moderators, I am probably not in the right place here. I wish for my account to be deleted. Whom do I have to contact?

It's not easy to simply thank someone for an answer or a tip, right?? Instead, it's always the others