Single-family house 1.5 or 2 stories - surcharge for multi-story?

Hello everyone,

my wife and I want to build a single-family house and would be very happy about tips and help.

I have a few general questions regarding the costs.

We are considering a 1.5-story house, rectangular footprint without frills/bays about 10x13 meters, foundation about 80 cm. Alternatively, a 2-story house would also be an option, where you could reduce the footprint to 10x11 meters.

Is there a rough estimate of how much extra cost one can expect for two stories in this case? Is it around €20,000?

Planned are a ventilation system, insulation around KFW 55 (our region sometimes has the highest heating costs, so good insulation makes sense here).

We also considered integrated roller shutters, what average additional cost can be expected for that?

Thanks in advance for your answers!


Key data

Region: Husum, Schleswig-Holstein

Roof pitch: 35-48° for 1-story, 22-35° for 2-story, permitted as gable/hipped half-hipped shed roof

Plot: 611 m², west orientation

Soil: completely flat, 40 cm topsoil, underneath sand/gravel (according to boreholes nearby), the challenge is rather surface water/drainage

Exterior walls are to be brick-faced.

Prefer solid construction, but I’m open to being convinced otherwise

Not much, actually. Some will even build the villa for you at no cost or cheaper. What does the development plan say?

Husum... can give you tips on BUs and GUs.

Roof pitch: 35-48° for 1-story, 22-35° for 2-story, permissible as gable/hip-cripple hip shed roof

So definitely no flat roof. Do the specifications all refer to the same property, or to different building plots of the same development plan?

Base height about 80 cm.

By that, do you mean a plinth under a raised ground floor, or a knee wall for an attic?

Alternatively, 2 stories would also be possible, then you could also reduce the footprint to 10x11 meters.

The reduction in footprint that a full story allows contributes significantly to keeping the price roughly in the same range.

What does the development plan say?

The development plan allows 2 full floors on all designated areas.

Do the details all refer to the same property, or to different building plots of the same development plan?

The data is the same for the entire development plan. Only the prescribed roof pitch varies between one- or two-story construction.

By that you mean: a base under a raised ground floor, or a knee wall for an attic?

I mean a knee wall, sorry for the confusion, this is my first house construction.