|To mark part of building, which has attributes, different from such ones at other parts|
|Used on these elements|
|Status: In use|
|Tools for this tag|
A way with the tag building:part=* describes a part of a building where some building attributes or the building function are different from the rest of the building.
How to use
Main article: Simple 3D buildings
Use building:part=yes for parts of the building which only have different attributes (building:levels=* and height=*). Use building:part=(type of building) for parts of the building which have a different function and possibly attributes (e.g. building:part=roof or building:part=retail).
In addition to the different ways tagged building:part=yes, there should be one area (closed way) marking the outline of the whole building, tagged with building=*. It is also recommended to use a type=building relation to group together the outline way and the building:part=yes ways.
Where a building has been split into parts, the whole building way should still have the tags building:levels=* and height=*. These values should be the maximum of all the building parts. A building that has a three-story part and a six-story part is still a six-story building.
Proposed additional tag
By using building:part=* the building parts can be mapped by vertical sections or horizontal "slices" or both concepts together. If you want to explicitly indicate which approach was used on this building, you can add the proposed tag building:parts=* (notice the "s" at the end) to the way marking the whole building.