Does adding ADU to 4plex change from residential to commercial?

[Account Closed]

This question may be specific to places like Portland where the city encourages density by allowing accessory dwelling units (ADUs) to be added to properties in residential zones.

If I purchase a 4-plex (zoned residential R2 in Portland) and rehab it to include an ADU, can I still finance with a residential mortgage? Because the permitting process is different to add an ADU vs a bonafide extra unit, and because SFRs with ADUs in Portland are still classified as SFRs, my hunch is that an ADU could be added to a 4-plex yet the property would still qualify as residential for lending purposes.

Anyone have any concrete knowledge about that? @Charlie Fitzgerald, do you know?

[Charlie Fitzgerald]

It becomes an SFR with an "outbuilding". Very little if any value will be given the "outbuilding".