Proposal talk:Accessory Dwelling Unit

Fragmented

It seems inconvenient to match, and disorganized to split them between detached=accessory and semi-detached=accessory for the same meaning. Only one *=accessory is needed. This avoids the building=* vs building=* + house=* issue at the same time.
A. residential=accessory (adapting to the building=residential sense, instead of landuse=residential )
B. residential:*=accessory ? (eg *:dwelling=accessory )
B. house:*=accessory ?
C. building:*=accessory ?
D. dwelling=accessory : There's exactly 1 dwelling=HMO House_in_multiple_occupation
—— Kovposch (talk) 07:56, 13 March 2025 (UTC)

Yes this is something that bugged me, but it also felt nice how it flowed off the existing keys.

A. I think this would conflict too much with residential=* since it's currently only used on landuse=residential and you can't really have a ADU landuse. I think dwelling=accessory could work, it would mean this dwelling is an accessory/secondary dwelling, or "accessory dwelling unit" ADU. It would then leave the option of dwelling=principal for the main residence, which while typically wouldn't be tagged, may be tagged where there is an ADU on the property. Aharvey (talk) 11:17, 13 March 2025 (UTC)

Resolved: proposal updated Aharvey (talk) 11:27, 13 March 2025 (UTC)

Interior ADU

Are above-garage and above-floor not handled by adding building:flats=2 to the same building=* ?
—— Kovposch (talk) 07:58, 13 March 2025 (UTC)

Yes good point. Aharvey (talk) 11:17, 13 March 2025 (UTC)

I forgot about the house=maisonette mentioned today https://community.openstreetmap.org/t/what-type-of-building-is-this-top-bottom-duplex/127320/
Maybe eg dwelling=principal;auxiliary , or dwelling:auxiliary=yes , etc, is needed to show the building=* has an ADU explicitly?
—— Kovposch (talk) 17:14, 14 March 2025 (UTC)

Resolved: proposal updated Aharvey (talk) 11:27, 13 March 2025 (UTC)

Auxiliary

I liked your suggestion of building=auxiliary in [1] for paralleling building=farm_auxiliary. While these buildings are just another kind of building=detached, so is building=farm etc. Taginfo shows very limited use of building=residential_auxiliary, which could be an option for distinguishing an ADU from a less substantial outbuilding. – Minh Nguyễn ^💬 16:12, 13 March 2025 (UTC)

That would be simpler, but less flexible. dwelling=accessory still allows you to tag the type of building so you could have a building=detached, building=cabin, building=static_caravan or a semi detached as an ADU. Not saying we shouldn't do building=auxiliary just it's less flexible. Aharvey (talk) 21:09, 13 March 2025 (UTC)

This has the disadvantage of inventing new building=* again. building=farm_auxiliary is defined as "on a farm that is not a dwelling". building=residential_auxiliary would seem to be for non-residential auxiliary buildings. If you want something building=* related, it could be building:dwelling=* or house:dwelling=* etc.
—— Kovposch (talk) 17:04, 14 March 2025 (UTC)

Other values for dwelling?

Will there be any other values for dwelling=*, other than dwelling=accessory? If not, wouldn't it be simpler to just use building=* + accessory=yes? --RuiM (talk) 19:23, 16 July 2025 (UTC)

The same question can be asked for your accessory=* , is it suggesting there's anything other than accessory=yes ? And yes, dwelling=principal / dwelling=primary can be used for what the ADU belongs to. accessory=* is context-dependent whether it's vehicle, electronics, and fashion accessories; or unclear whether it can be used to mean there's no ADU here, instead of this is not an ADU.
—— Kovposch (talk) 21:20, 16 July 2025 (UTC)