Per GWR house numbers are assigned to (building-)entrances in Switzerland so neither to the plot or the building.
However there are a couple of things to note:
- not all cantons and municipality have all the necessary data (yet) in the GWR. For example the canton Ticino. In such cases the house number(s) are located on the building centroid.
- there continue to be buildings that should have a full address assigned, but which only have a place/street value, typically farms.
- and yes I could point out that swisstopo has managed to muddy the waters more than they already were, but lets ignore that.
There’s no real harm in having non-address house numbers. Matter of fact I have historically added them in Zürich because there are a fair number of cases where the ancillary buildings have a non-suffixed number (42) and the residential building is suffixed (42a) and it is then very confusing if you don’t map the non-suffixed number.
In any case lots of cantons and municipality didn’t assign house numbers to ancillary buildings before 2019 and they now use numbers with a dot in them (NN.N), with other words these are easily detectable.
Simon