3D-tagging of simple houses with just dormers

Hey guys!

I’ve been tagging roofs and buildings with 3D tags for quite a while now and ever so often, I come across a simple house with a roof with just 1 or 2 dormers and nothing else. Read: if it wasn’t for the dormers, then I wouldn’t even need to use building parts. When tagging such a building, I have 3 options:


  • Option 1: If I only add the dormer with building:part=yes to the building, the rest of the building won’t be rendered. Which is correct by definition. Doesn’t work of course.
  • Option 2: If I add another building:part with the same outline as the building itself, this is flagged as an error by JOSM, because we now have 2 ways with the same outline.
  • Option 3: If I add a building:part=yes to the building=detached way, JOSM complains that a building cannot be a building part at the same time.

I’m currently using option 2, but I’m wondering, if there is a better, JOSM-error-free way of achieving this, or whether I should probably flag the warning as a potential bug to the JOSM developers.

Option 2 is correct mapping and there is no better way. (There are probably JOSM-error-free ways, but they’re not better.)

Unfortunately, I’ve found that the warnings of JOSM validator are often incorrect when doing 3d mapping or indoor mapping. If you feel like creating an issue in the JOSM bug tracker, that would be helpful.


I went ahead and created a bug report.


Thank you! Do you still have the example building so that you can upload it as an .osm file like Klumbumbus is asking on that bug report? If not, I could also create one from scratch.

Just uploaded it. Should have logged in and tracked the bug. Meh…

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