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I've been tracing buildings using separate areas for different roof levels as recommended on the wiki.

How should I go about tagging them and signifying that they belong to the same structure?

Here's an example:

alt text

If I were to just paste the same tags onto each shape, it would look like there were multiples of the same building. What do I do? Should I be using some kind of relation?

asked 20 Jun '11, 00:43

Sekai's gravatar image

accept rate: 0%

edited 20 Jun '11, 00:44

That recommendation on the wiki is not necessarily widely accepted. I can see the interest in rendering different roof levels from those with an interest in 3-D rendering.

It is acceptable to draw a single outline for the collective building. Where it is attached you could reasonably call it one building, and tag it as such.

If you wish to show more detail, including the multiple roof levels, a multipolygon relation is the way to go.

  • Draw the multiple, adjacent polygons.
  • Create a relation, type=multipolygon
  • building=yes
  • addr:housenumber=123
  • addr:street=Sesame Street
  • name=as appropriate
  • amenity=university; or other as appropriate
  • make each individual building outline a member of the relation, with role=outer

That should do it.

Those interested in 3D rendering will probably suggest tags for the various roof levels as well. Incomplete or contentious examples may be seen here.

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answered 20 Jun '11, 01:11

Richard%20Weait's gravatar image

Richard Weait
accept rate: 17%

Thanks for the clear explanation! Am I correct in thinking that only the relation should be tagged and not the individual polygons? (as long as the tag relates to the building as a whole)

(20 Jun '11, 18:34) Sekai

Yes, you do not need the tags on the building ways if you have them on the relation.

(20 Jun '11, 19:10) Gnonthgol ♦

This multipolygon relation would be invalid because the outer rings must not share paths. See

Map the building accordingly

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answered 22 Apr '21, 17:31

Robhubi's gravatar image

accept rate: 0%

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question asked: 20 Jun '11, 00:43

question was seen: 7,059 times

last updated: 22 Apr '21, 17:31

NOTICE: is no longer in use from 1st March 2024. Please use the OpenStreetMap Community Forum