Questions about house construction - Tips from experienced builders

Hello everyone,

I am new here in the forum and hope for some helpful tips. We are currently planning a single-family house and have already purchased the plot. At the moment, we have some offers from prefabricated house providers as well as one from a solid house provider (here it really is the case that the prices are not that different). The crucial question is, that the stated price is usually not the final price.

Now my question is, how much additional cost can be expected, just for the house? Our current cost plan looks like this: house 230K€, land 70K€ (fully developed), incidental construction costs 30K€ – is this calculation sufficient?

Single-family house 150 sqm, 1 1/2 stories with KN 1.80m, floor area 9 x 10 m (house) – does this even make sense on a plot of 22m x 22m? We want to build without a basement, so we need storage space. Ground floor: living room, dining room, kitchen, utility room, guest room, WC/shower – upper floor: 2 floor plans. Children’s room, bedroom, bathroom with a 1/4 turn staircase (other ideas maybe on this?). How large should a utility room be designed, the technology is gas boiler with ventilation system and solar heating support ... (I have read the various opinions on the heating topic, for us it is also a monetary decision. Please no fundamental discussion here). All the subsidies for heat pumps are totally overrated, we are building in Bavaria, where there is the 10,000 houses program, which was already reduced in benefits one week after the new kfW subsidies started!!! Since all the programs overlapped ... (headache)

What do you have to consider already in the preliminary planning aside from surveyor, soil report, house connections, etc.?
Please give some suggestions on what you have to think about, or what is usually not considered early on and then still happens.

Many thanks in advance. Charly

Read this thread and apply what you have read. Then it will be easier to answer many of your questions, especially about the floor plan you can't say anything without a floor plan, let alone about the stairs.

Cost plan looks like this house 230K€, land 70K€ (fully developed), ancillary construction costs 30K€ - is this calculation sufficient?

Tight. You should calculate with 1600 per sqm.
What about the additional purchase costs for the land?
The ancillary construction costs are also tight but could work. Better to calculate 10 more.

What about the garage? What about the outdoor facilities?

Land size can fit, depends heavily on what demands you have for the garden; or how the building plot looks like.

At 9mx10m you don't reach 150m2 except clearance if you build without walls.

Has a knee wall of 1.80. That makes 180sqm walls

Well, I can tell you we have a 10x10 house and a 2.30m knee wall, and we have about 154 m2. But there are also different area calculations.