It has all already been discussed in detail, but here is still a thought from me that is often not considered. That the children grow up is a natural state. All parents think that the children will then simply continue living "upstairs." Then one should not forget to plan the property as a two-family house right from the start. If you elegantly build, for example, a staircase going up from an open hallway or something similar, it is forgotten that children are independent, have visitors, etc., which one does not always want to be affected by. Often, the adult children still want their own house!, because they do not always want to see their parents ;) because then they see what they could become! As a result of the astronomical land prices, a second house is often desired on the property, and the floor area ratio often becomes a problem. Not all plots are so elegantly dividable that enough square meters remain for the "children's house." I had built "arrogantly," but now realize that I do not need all the space and therefore my now grown child can only build a dollhouse on the remaining plot. Therefore, consider beforehand whether a second house might be built in a few years (time passes quickly) and therefore remember that the floor area ratio plays a major role. A bit smaller and instead more space for another little house!? I apologize for the irony but could not withhold this thought for builders with children, even if it does not apply to many. Wishing all planners much success and fun with children who grow up on their own (very quickly)!