насколько знаю, без type=building в таких рендерах как kendzi3d (Josm) и
osmbuildings.org здания отображаются не правильно - на скрине - школа в Измаиле
If at least one part of a building is hanging over the building footprint or if the building has a complex structure with lots of parts, a type=building relation can be used to group the building outline and all building parts together. Otherwise, there is no need to create a type=building relation, i.e. simply position all building parts inside the building outline as described above.
If the type=building relation is present for a building, all building parts must be listed as the relation members with the role part. The building outline must be listed with the role outline. The building parts can be located in any possible way (inside, outside, intersecting, touching) relative to the building outline in the presence of the type=building relation.
If there is no type=building relation, an application should treat all building parts within the area of the building outline as part of that building.