Talk:Tag:building=annexe

building=outbuilding

Wouldn't this be a building=outbuilding? How does it differ from a building=outbuilding?

building=outbuilding is defined as a less important building near to and on the same piece of land as a larger building, which seems to imply that it could be any number of things from an annex to a shed to a farm stand building, An annex is a building that can be lived in. Does the annex definition need more clarification? Glassman (talk) 18:49, 14 August 2024 (UTC)

So, an annexe is a type of outbuilding? Do they have separate housenumbers than the main building? --Westnordost (talk) 19:27, 14 August 2024 (UTC)

Structurally, "annex" in general is often/sometimes attached directly. Outbuildings are usually not attached. How do you differentiate attached vs non-attached annexes?
—— Kovposch (talk) 06:46, 10 January 2025 (UTC)

No separate housenumbers - the same address as the main house. I am documenting the annex because these are becoming more numerous in cities with housing shortages. It would be good to help document this type of building. Glassman (talk) 19:55, 14 August 2024 (UTC)

They may or may not have seperate house numbers. This shouldn't be a blanket rule. The owner might just put up a new letter box with 5A for the granny flat, where the main building was 5. Doesn't need to be an officially assigned address for the letterbox and address to exist. The key here is they are a small dwelling on the same lot/parcel of land as the main building, and not a strata/community title (sorry I'm using Australian specific terms here). Aharvey (talk) 12:28, 8 January 2025 (UTC)

Neither of them is good. They block the actual structure or use from being recorded. building=outbuilding was imported. This building=annexe was mass added in 2017. You need to check how it was actually used, or propose your own definition. https://taghistory.raifer.tech/?#***/building/annexe
Eg building:outbuilding=yes / building:annex=yes would be better to follow building:prefabricated=* for extending. Or eg building:role=main vs building:role=outbuilding / building:role=annex , and add building:outbuilding=* / building:annex=* to the building:role=main to show whether it has outbuildings/annex.
—— Kovposch (talk) 06:40, 10 January 2025 (UTC)

Not sure what you mean. Annexe/ADU/Granny flat is the structure and use, a smaller unit dwelling building on the same property/lot/parcel as another main residence. If it's a garage, it's not an annexe, if it's a static_caravan, it's not an annex. It falls under the same classification as detached, semi-detached, terrace, etc. Aharvey (talk) 10:49, 10 January 2025 (UTC)

This is why the word is unsuitable. "Annex" buildings can be found in all other building types. Users may be inclined to use this for all annex buildings, to show they are less important a main building.
The mass addition was in Spain, with someone changing building:part=* to building=annex . They are mostly in urban areas, wall-to-wall connected, and forming a chain of several buildings. The meaning is certainly not what you assumed. https://www.openstreetmap.org/way/435684867/history
There are many building=annexe are around Cologne in Germany now. Their use need to be determined. There can be multiple of them connected to the main building=* , even larger than it. 116952850 116952850
—— Kovposch (talk) 06:50, 11 January 2025 (UTC)

Is this for self contained living within an existing building or only detached residential?

Further discussion at https://github.com/openstreetmap/id-tagging-schema/pull/1422 Aharvey (talk) 02:19, 11 January 2025 (UTC)

Using this tag for ADUs conflicts with pre-existing usage

Thank you for looking for tagging for ADUs. These have been popping up in my area and I wondered how to tag it; I ended up using the local term (building=house + house=laneway_house) but my usages are so few that this would be easily retagged to an accepted worldwide tag.

I share concerns raised by Kovposch above:

• Per history chart, most usages of this tag are from 2017 when there was a major import/retagging, yet the wiki was only created in 2024
• There are examples of usage that do not correspond to how it was defined in wiki in 2024, including https://www.openstreetmap.org/way/435684867/history apparently tagged as part of the 2017 retagging - it is very clearly not an ADU in American/Australian/Canadian sense
• As another example, https://www.openstreetmap.org/way/660755738/history was retagged to annexe in 2021, but its previous tag indicated it is a service building, not residential (the name "budynek gospodarczy" includes something like a shed, storage, workshop or similar)

Personally I am in agreement with matkoniecz on Github that tagging by purpose should be adequate, so building=detached or building=house, and then it could be narrowed down with house=* if desired. We could probably do worse than house=adu or house=accessory_dwelling or house=secondary_dwelling or something or maybe even house=annexe_dwelling if you want to go British (are there ADUs in Britain?). But in the end sometimes it might not be possible to tell if a residential building is an ADU or not, so tagging that does not depend on being able to make this distinction while allowing the distinction where possible would be good - building=* + house=* is one way to do that.

By the way, some ADUs in Vancouver do have house numbers, 8400781795 8400781795 for example. (House numbers in Vancouver usually aren't consecutive, so the missing numbers can be assigned to newly constructed laneway houses. I do not know if they get direct mail delivery to the laneway house - I would guess not.)

The discussion on Github mentioned the issue of "self-contained" residential units "within the main house" but I believe these are outside the scope of OSM since they're within one building and it's not clear it's possible to reliably distinguish them even from street-side survey. If anything, a tag like building:flats=* with the number of units in the building appears more easily verifiable (government records, or visible number of mailboxes, or number of electric meters or gas meters in regions where those are usually visible from the street).

May I also suggest that going through with a proposal or a discussion on the forum may have helped to uncover these issues before making a request to add a preset to iD? --Jarek Piórkowski (talk) 02:19, 14 February 2025 (UTC)

https://www.openstreetmap.org/way/660755738/history and other buildings from that edit is now fixed (if bad data is spotted it would be quite useful to fix it or create a note) Mateusz Konieczny (talk) 13:17, 14 February 2025 (UTC)

You've convinced me. Interior self-contained residential units can be either ignored as being outside the scope of OSM, or tagged with building:flats=*. I opened the preset PR on the basis of this wiki documentation, but I've sinced closed the PR since it became apparent that this wiki documentation is problematic. I've now opened Proposal:Accessory_Dwelling_Unit and welcome feedback.Aharvey (talk) 06:18, 13 March 2025 (UTC)