add building=annexe

[andrewharvey]

Description, Motivation & Context

building=annexe is currently in use and documented on the wiki.

Ideally we would have a tagging preset for this tag to make it easier for users to add, and to translate into local terms.

Links and data

Relevant OSM Wiki links: https://wiki.openstreetmap.org/wiki/Tag:building=annexe

Relevant tag usage stats: https://taginfo.openstreetmap.org/tags/building%3Dannexe

[github-actions]

🍱 You can preview the tagging presets of this pull request here.

[andrewharvey]

🍱 You can preview the tagging presets of this pull request here.

Looks good!

[1ec5]

The name needs to be in American English, but “annexe” is completely unknown to American English speakers. In California, the formal term is “Accessory Dwelling Unit” (hence ADU), but this might be unknown in other parts of the country, compared to something more crass like “in-law unit” or “granny suite”. I suggest asking folks in the #language channel of OSMUS Slack for second opinions.

[andrewharvey]

I'll use "Accessory Dwelling Unit" for now. Translators can choose the best term for their region.

[1ec5]

By the way, thanks for posting this – it’s a frequently asked tagging question in Slack, but I can never remember the tag.

[tordans]

For documentation: I was wondering how to translate this key into German.

ChatGPT suggest "Nebenwohnung" and "Einliegerwohnung"

Full ChatGPT Answer

In the context of OpenStreetMap (OSM), finding an accurate German translation for "Accessory Dwelling Unit" (ADU) is important to align with how such structures are referred to in German-speaking regions. Here are three possible translations:

1. Nebenwohnung

   • Literally means "secondary dwelling" or "auxiliary apartment."
   • Suitable for describing an additional residential unit on the same property, but it may imply a detached or attached nature.

2. Einliegerwohnung

   • Common in German to describe a separate dwelling unit, often within a larger home, such as a basement or an annex.
   • Best suited for ADUs that are part of or attached to the main house.

3. Zweckwohnung

   • Translates to "purpose-built apartment" or "auxiliary apartment."
   • Used less commonly but can describe a unit intended for specific use, such as a guesthouse or rental.

Recommendation:

The best term depends on the type of ADU:

• For a detached ADU, Nebenwohnung fits better.
• For an attached or basement-style ADU, Einliegerwohnung is the most widely recognized and appropriate term in German-speaking regions.

Since Einliegerwohnung is already well understood and aligns closely with the concept of an ADU in residential settings, it is likely the most suitable option for OSM purposes.

However, Nebenwohnung seems to be a synonym for Zweitwohnung which is a term used for something different. https://de.wikipedia.org/wiki/Nebenwohnung

So Einliegerwohnung https://de.wikipedia.org/wiki/Einliegerwohnung seems to be the better term. However that suggest that the second place is part of the same house, not detached (like ChatGPT suggested as well).

Aus der Funktion als untergeordnete Wohnung ergibt sich, dass die Einliegerwohnung keinen direkt nutzbaren Wohnungszugang vom Freien aus hat, denn sonst wäre sie als zweite Wohnung im Wohnhaus anzusehen.

"Nebenhaus" would be the fitting term, but that is not used in this context but describing the neighbours house.

The tag is used ~200x in Germany https://taginfo.geofabrik.de/europe:germany/tags/building=annexe#overview so someone has to know what it means :-).

[tordans]

As a review note: Did someone check the Info-i (Wikidata item)? https://github.com/openstreetmap/id-tagging-schema/blob/main/.github/PULL_REQUEST_TEMPLATE.md?plain=1#L51-L62

[1ec5]

By the way, I mistakenly thought “annexe” is a term of art as opposed to a different spelling of “annex”, which is in fact familiar to American English speakers. But based your interaction with ChatGPT, I now get the impression that this is just a typical OSM English narrowing of a term that’s broader in the real world.

At least in American English, an annex is inherently attached to the building and typically smaller than the main building, and it doesn’t necessarily have anything to do with residential occupancy. For example, this city hall used to have an annex joined by a breezeway. By contrast, an accessory dwelling unit is literally a residential building. Most ADUs aren’t connected to the main building, or at least aren’t connected to the main living space, because the in-law, granny, or renter would want some privacy. Many of the ADUs I’ve mapped are far larger than the main building.

Are we sure the wiki is correct in associating building=annexe so strongly with ADUs, and that usage is consistent? The English wiki page was created in response to this Slack discussion about ADUs and a talk-gb thread that found “residential annexe” and/or “detached annexe” to be an appropriate British English term for ADUs, but no German mappers were involved in those discussion as far as I know.

[andrewharvey]

The best term depends on the type of ADU:
For a detached ADU, Nebenwohnung fits better.
For an attached or basement-style ADU, Einliegerwohnung is the most widely recognized and appropriate term in German-speaking regions.

Interesting. In Australian English, an isolated living quarters within a detached house would be "self contained accommodation" ie. a basement, lower lever or upper level which you access from a separate entry door to the main living quarters. Sometimes these are converted or added after to rent out while you're still living in the main residence. Typically this wouldn't be mapped at all in OSM though as it's more to do with an internal residential building configuration.

The "detached ADU", in Australian English is "Granny Flat" and it's a detached building not connected or part of the main residence, but on the same property/parcel/lot. It's distinguished from the main building by being smaller/secondary. You could map these as building=detached, but they are a bit different and it's good to capture this via the building=annexe tag.

Are we sure the wiki is correct in associating building=annexe so strongly with ADUs, and that usage is consistent?

Yeah, maybe not. It may be best to hold off on this PR then until the tagging is clarified.

From Google "an annex is a self-contained living space", so it sounds like it might cover anything from self contained living inside an existing building (eg. the lower/upper floor or basement, or even just a room blocked off from inside access and with it's own dedicated external door), or a building added on adjacent to the existing building with a shared wall, or a completely detached building.

Perhaps then we need something like building:part=annexe for an addon to a building to create a self contained space and building=detached_annexe where it's completely detached and for residential use, eg. ADU/Granny Flat.

[matkoniecz]

I am confused why building=detached is not preferred tagging here, possibly with extra tags

https://wiki.openstreetmap.org/wiki/Tag:building=annexe has

Distinction from building=detached
A detached house typically has an official address where the annexe might not.

so if legal change happens (it gets address assigned by legal authority) its building type changes?

[andrewharvey]

I am confused why building=detached is not preferred tagging here, possibly with extra tags

detached=main, detached=secondary. At first that sounds okay, however I don't think it's ideal, as then it's ambiguous if building=detached is main or secondary, and therefore you would expect every building=detached to also tag a detached=* value, given the vast majority would be detached=main this would be undesirable. Further based on my examples below, a secondary dwelling may be detached from the main building or attached to it or within in, so it's not correct to say they are all detached.

---

Stepping back I tried to look at this again from a fresh perspective.

In Australia we have a concept of a "granny flat", however in official documents this is also referred as a "secondary dwelling", which from everything I've read is the same concept as the ADU/Accessory Dwelling Unit term used in the US. This also matches the current OSM Wiki documentation of building=annexe "A small self contained apartment on the same property as the main residential unit."

A granny flat is a self-contained secondary dwelling that can be attached to, within, or separate from the main house.

Breaking that down, you have the the functional requirements:

• self-contained ie. a living space that has it's own facilities like a toilet/shower/kitchen that aren't shared facilities.
• secondary not the main dwelling on the property (the main property would be called the Freestanding House), and by property I mean the land parcel/cadastral parcel/lot/title.

and the physical properties:

• attached to the main house,
• within the main house, or
• separate from the main house

attached to or within may be hard to tell, for example a basement or attic secondary dwelling would be considered within, but a building build on the side of the house, sharing a wall would be attached, but other times it can be hard to decide.

Example of separate from the main house:

Example of either attached to or within the main house:

Tagging those within or attached to the main house is difficult and it's hard to survey, so I'm mostly just thinking about the "separate from the main house" scenario here. That said building:part= as I suggested previously could work in this example.

[andrewharvey]

We also have https://wiki.openstreetmap.org/wiki/Key:house which applies to building=house. Under that tagging scheme I would consider then building=annexe (secondary house) + annexe=detached (for a free standing annexe/secondary dwelling/adu/granny flat) to be appropriate.