Why building a house almost always costs more than calculated

Starting from the first thought or from the financing commitment?

110k difference between "before planning" and "end of planning including sampling"

I think everyone has understood that well enough now...

I assume you are referring to the post by . Why do you address him when he explicitly asked again for clarification and explanation? (at least that is how I perceive your post)

We also have over 60k in additional costs, and this is with a developer project. The main causes are the kitchen, bathroom, and electrical.

What exactly, aside from the kitchen itself, caused the costs for the bathroom, electrical, and kitchen to balloon so much?

So our construction is currently (shortly before moving in, but still some way to full completion) overall about 5% more expensive. The three biggest cost drivers were:

[*]Wall tiles in the bathroom were forgotten, somehow they disappeared from my calculation during the planning process. Including installation, this added a small four-figure amount ("inaccurate detailed planning").

[*]KNX was planned afterward: It was actually ruled out before for cost reasons, but then we decided to include it after all, in the topic "You only build once".

[*]The kitchen then also became €3,500 more expensive due to "You only build once" than originally planned, but it turned out really great.

The rest were then small things, for example, we chose a different impact sound insulation, or yesterday I had to buy additional parquet because we had significantly more waste than originally planned. It all adds up to a substantial total amount.

What has the fun with KNX cost you? Although I assume it will still consume a lot. Once you start with it, you find 1000 ways to add this or that. Even if it’s the cool room controller with voice recognition.

What did the fun with KNX cost you? Although I assume it still swallows a lot of money. Once you start with it, you find a thousand ways to add this or that. Even if it's just the cool room controller with voice recognition.

Oh yes, quite a bit more will be added over the next few years. The budget is currently around €6,000 just for the KNX components. In total, the electrical installation costs around €16,000 and we are doing quite well with that so far.

But then that's already not just a little bit KNX