To mark number of levels above ground level
This tag is used for marking the number of levels above ground level of a building (building=*) or part of a building (building:part=yes). If a building consists of parts, which have a different number of levels, but the same height or the same number of levels, but different height, then it is useful to add the tag height=*.
- P + S counts as building:levels=2
- K counts as building:levels:underground=1
- D counts as roof:levels=1
Buildings that don't start at ground level
If the bottom level of a building or part of buildings starts not from the ground level, we use the tag building:levels as a value number of levels, which building or part of building virtually has, if we think, that space between ground level and bottom level of building or part of building is filled by levels, which have height, equals to medium height of really existing levels. For describing number of values, "filling" space between ground level and bottom level of building or part of building, we use tag building:min_level=*.
For building we use number of levels, which is maximal for all parts of building. For example, if building consists of parts, which have 2, 3 and 4 levels, we use building:levels=4. For describing number of levels at parts of building we use building:parts=* at polygon of building and building:part=yes and building:levels at polygons of parts of buildings.