One more thing on the topic:
We have not actively saved for the house construction. Through our condominium [ETW], we have virtually saved passively and also benefited from the value increases of the past years. Additionally, we had a large surplus every month and invested parts of it. This allowed us to now go into the house construction with a high equity share.
Regarding the house construction, I would simply start nowadays regardless. The price increases on the market exceed the interest rates for borrowed capital by a large margin. With an assumed price increase of 3% per year, after 5 years, thanks to compound interest, there are 16% additional costs. For a house construction costing over 500k, it costs 80,000€ to wait 5 years to save.
If I am able to save 20k per year, we are talking about 100k equity that can be saved during this time. So, one is actually only 20k in the plus...
If I simply take the 100k additionally as a loan, I may have to pay about 15k more in interest depending on the initial repayment.
Quite simplified, but from a financial point of view, saving currently is not really worthwhile... assuming creditworthiness.