Building merge parts

How to find and merge diffrent parts of the building, if there is no building relation tag. For example this one: 120 Wall Street (https://www.openstreetmap.org/way/278076374#map=19/40.70476/-74.00595)

Short answer …

Find: All bullding:parts within the building shape belong to the building.
Merge: Not necessary for 3D modelling and not commendable due to possible side effects.
Building relation tags: Not always needed.

see http://wiki.openstreetmap.org/wiki/Simple_3D_buildings

These postings were before:

http://forum.openstreetmap.org/viewtopic.php?id=52993

Why?:
http://demo.f4map.com/#lat=40.7053533&lon=-74.0056745&zoom=19