Single-family house with basement in NRW - is our financing solid?

Hi - I’d like to pick this up again: We have a concrete offer for the house, as well as for the basement, for the demolition. Those are probably the biggest chunks for now. Notary fees for the land division and transfer will be incurred, house connections and outdoor facilities we may not have estimated very high, whether the kitchen will come in at 15k€ remains to be seen – but where does the assumption/claim come from that we have easily miscalculated by

100 - 120k

? I can still understand planning for 20, 30, or even 50k€ more, those “add up” quickly through special requests, but over 100k€? What cost factor do you think I’m overlooking here?

Secondary construction costs, earthworks, possibly soil replacement. Landfill costs (Have you already conducted a soil survey?), development (During demolition all pipes must first be disconnected and then reconnected, can the branch from the main line be reconnected to the same place or does it have to be laid elsewhere?) are all roughly estimable costs and surprises during demolition (asbestos) or in earthworks and foundation work especially on slopes can always occur. Then upgrades, is the standard really sufficient? Some people lose your 50k alone in the heating & plumbing trade for upgrades (but that is extreme).

Some say as a rule of thumb just add a 20% buffer on everything. Then you’ll get there...

Believe me, 50 K accumulate quickly without the need for any major special requests. Of course, it is hard to say where additional money will have to be invested in your case, but just calculate with the often mentioned 2,000 EUR per m² of living space: For 189 m², I already come to 378,000 euros. This amount applies plus floors, painting work, any special requests (controlled residential ventilation, brine-water heat pump, aluminum roller shutters, KNX, ...) as well as plus the basement and of course the usual additional costs. It has already been mentioned that the basement presumably will not be available for 65 K – otherwise, there is probably simply a lack of equipment there again, which you take for granted but the provider would like to have paid for separately.

No one here benefits from criticizing your building project, but you can avoid your planning falling apart at both ends.

Just an idea: Have you also obtained a second offer?

The risks regarding demolition and disposal are by the way not even "standard" yet, so they will still be added on top of the big pile as explained by .

I think that despite the rather rough calculation of the income, such a project is feasible with this and the available equity – the size of the house with a basement, etc., certainly speaks for higher construction costs. Careful calculations would be necessary here, as well as for the income and the projection into the coming years. The house would "discipline" – introduce "forced saving." The desired vacation would no longer be the priority, but the desired house – and the vacation would depend on what is still feasible. So a project that roughly costs ~600,000€, with 120,000€ equity and at least 5,000€ income sounds doable.

Caution, the basement is included in the 189m². So do not calculate it twice.

2. We definitely plan at first completely without cost-reducing own services on the house.

Which cost-reducing own service are you thinking of? First, you have to get from the turnkey house to a habitable house. Painting work and floors are at least missing, possibly more depending on the scope of construction services.

That alone costs a few thousand euros if done as your own work, and if you have it done (very likely because of children) it costs five figures. So there is nothing to save at first.