[pedrocr]

The sane solution for that is to just use "number of meters since start of street" as the building number. That way you can always fit new buildings between existing ones and get the bonus that if you are at building 100 and want to get to 200 you know that's 100 meters away. Usually you'd also do even numbers on one side of the street and odd on the other to make it easy to know which side to look at. This means you can't have doors closer than 2 meters apart which is usually ok. If you really need more doors then 100A and 100B are the usual hack.