Additional construction costs and realistic additional construction costs?

Hello,
we have planned to build a single-family house 9x11m with geothermal heating on an 840sqm plot. According to the municipality, the plot is fully developed.

For this, we need a very spacious double garage of 10x7m

the house costs + some extras amount to 185,000
For the plot, we pay 70,000 including property transfer tax and notary fees

now comes my question

for the ancillary construction costs:
construction electricity,
construction water,
additional earthworks - here we have about 1.5 meters difference in height within the building area -
soil survey,
re-surveying by the cadastral office,
electrical extras,
floor coverings,
building permit,
outdoor facilities (materials only),
wood stove
double burden
materials for the garage (completely self-performed)

I have planned about 65-70,000 for this

the kitchen comes separately.

do you think that will be enough?

I don’t want to have to finance an additional 20,000 in the end, so I’d rather plan for more from the start if necessary.

thanks,
mukkel

Your garage is almost the size of my house. You want to build it without (Baugenehmigung) structural analysis? 65k€ can be enough but doesn't have to be. For all your items, there are ranges. Take the wood stove. It is available for 3k€ and for 10k€,... So have quotes made for all items where possible. Especially the earthworks cannot be assessed without knowing the property and the region.

So...
Wood-burning stove 5-25 k€ (depending on preference)
Electrical extras 0-100 k€ (depending on preference)
--- so the range is from 'might work' to 'no way ever'.

Earthworks: depends on the plot, soil, excavation material, excavation volume, etc. Fortunately, our plot is fairly level, but the material is not suitable for backfilling. So roughly 10k€ extra beyond what was planned.
Sewer connection - means "fully developed" here: Is everything in the street, or is everything already on the plot?
If the former: Sewer connection for us: 15 k€ + everything that then happens on the plot (inspection shafts, transfer shaft, sewer works). We probably do without a sewage lifting station - otherwise the next few k€ from the reserve are gone. Electricity, water, telecom also need to be added.
Floor coverings: 50 - 150 €/m². Depending on preference.
Outdoor facilities - material costs from 15 to 150€/m² - depending on preference and required area (don’t forget substructure costs!).
Garage: depending on preference - metal box 3k€, luxury double garage 50 k€ - everything in between is possible.
Double burden - how should one assess this - when do interest and repayment start, how long does the double burden last, how high are rent + additional costs?

For our plot: 65k€ is definitely not enough here.

Is the house with 185000 already calculated by a contractor or are you working with catalog/web data? Because then 185000 quickly becomes 210000... Chimney for example, ventilation... there are many things that are not included in a catalog house. A car is also offered with a base price: air conditioning, different paint, and a few highlights easily make the price 20% more expensive, same with the house. The additional electrical work and floor coverings are then equivalent to the necessary doormats and safety set. Baier has already written about the development costs of the utility providers. Who wants a 70 sqm garage? A parking space is 15 sqm...

The fireplace costs 2000.
The building application for the garage will be made together with the house, the structural analysis is done by a friend of ours, he is a structural engineer himself.
10,000 for house connections, 10,000-15,000 extra for excavation and filling.

On the property itself, two black pipes are sticking out, nothing more. There are no covers or anything to be found.

By electrical extras I mean additional outlets. I planned about 500 euros for that. We have tile prices, that’s more than enough. We will lay them ourselves completely (not for the first time). Same for laying laminate.

The maximum cost for the exterior facilities stone is 15 cents. With the square meter amount of the driveway + gravel + joint, we also come close. We will bring terrace slabs with us. We already have a large garden at the current apartment.

Well, double burden? Good question. I estimated about 5000 for that. It depends on which developer we decide on. One needs 12 months for everything, the other only 7... but is also 20,000 more expensive.

Questions upon questions...

The office doesn’t say much, the developers only estimate so far as long as we don’t sign. If I get prices myself for everything, then I might as well build with a freelance architect, because I would basically do everything else myself.

That is already all calculated with all extras such as chimney, electric aluminum shutters etc., more windows, different front door, floor-to-ceiling shower, different roof tiles, special clinker bricks and and and