Costs of different house types

Hello everyone,

I have just started to read up on the topic of "building a house," even though the desire for it is still quite vague at the moment.
This will rather be a project for the next 5 years. I feel like I’ve already spent dozens of hours here in the forum :)

I am currently trying to get a bit of a feel for what makes a house expensive, what is energetically unfavorable, etc.
That’s why I’m interested in whether there are rough guidelines for comparison.
Disclaimer: I know that it always depends on the specific personal situation. Nevertheless, I could imagine that certain rules of thumb have become established.

[*]First of all, I would like to know: how does a bungalow compare to a house with 2 full floors? (In terms of costs and the effort to achieve a KFW level). My youthful recklessness tells me that a bungalow is cheaper to build, but more expensive in insulation due to the larger base/outside surface.

[*]The same question applies to a 2-full-floor house compared to a 1.5-floor house (I know, this doesn’t really exist ;-) ) with knee walls, without an attic.
An attic is of course great for storage, but initially also wasted space that requires another intermediate ceiling and more exterior surface.

[*]I also like the idea of an L-shape (living room) with a terrace enclosed in the inside corner.
Does the deviation from the cube shape significantly impact the price? I would assume that especially if you want Kfw certification, this might be difficult because corners are probably complex to insulate. Or are these rather minor issues?

[*]The same question arises for dormers and possibly third or fourth gables.

[*]To what extent does the roof pitch affect price/energy efficiency? (Assumption: a flatter roof uses less material and also exposes less surface area).

Again a disclaimer: my goal is not to plan the cheapest possible house. Nor do I want to optimize every decision for Kfw (I don’t even know if I want or need Kfw).
I am just trying to get a feel for how building decisions affect costs and energy efficiency. After all, I don’t want to plan something utterly unrealistic. When it gets more concrete, of course, an architect will be consulted.
Until then, I want to gain some background knowledge.

Thanks & best regards from the cave.

Welcome to the forum, your relatively general questions will be answered just by reading along, in short the more complicated the house, the more expensive. Generally, the plot dictates the house, plot size, building regulations, developer, neighboring buildings, slope yes/no, nice view, etc. When the time comes, present the plot with the completed questionnaire and some will advise you.

A bungalow is definitely more expensive in many respects (probably not from a KfW perspective):
- larger foundation slab
- more roof

But it also has many advantages:
- no stairs (except to the attic -> storage space rarely used)
- with the installation of a rainwater cistern, you get much more water yield
- larger roof area for a photovoltaic system
- faster to build than a two-story house since you don’t have to lay screed on the attic and one drying time is eliminated.

From a KfW perspective, it probably isn’t much more expensive than a two full-story house, since the number of walls (sqm) is probably the same, resulting in similar costs. But this is a layman's assessment. There are surely more and better experts :cool:

Generally speaking, building upwards is always cheaper than building outwards. 1.5 or 2 stories makes no difference.

You have recognized the price drivers well. The biggest problem will be your lead time of 5 years if the price development continues like this.

Faster to build than two-story buildings because you don't have to lay screed in the attic and one drying time is eliminated.

Faster to build is true, but the reasoning is nonsense because the screed is laid all at once and then dries in parallel. Or did you mean the drying time of the ground floor ceiling? That, of course, only applies to conventionally built houses. In timber frame construction, that doesn't matter. Otherwise, I go with geometry: The most economical building shape regarding the ratio between surface area and volume is a sphere – but that's hard to build and live in, so the next best option is a cube. The more you deviate from that, the more exterior surface you have to create for the same volume (simplified: living space). Seen that way, a classic two-story building (with a flat roof) is already close to the optimum. However, many other factors and details come into play that distort this seemingly simple picture considerably, so I have mostly oriented myself by what I find visually and practically appealing. In the end, the price differences are not as huge as one might think.