The Difference Between a Companion Unit + an Accessory Dwelling Unit

By Sean Canning

In this video, I want to describe a couple of terms that come across my desk pretty frequently and explain the differences between them. They all relate to Accessory Dwelling Units or ADUs.

Over the years, there has been a lot of confusion as to what several terms mean related to ADUs. You have probably already heard of many - Granny Flats, Companion Units, Guest Homes, Pool Houses, Casitas, etc.

In the previous versions of the city of San Diego's code, oftentimes Accessory Dwelling Units were being referring to at us as Companion Units, and vice-versa. The terms were used interchangeably, causing quite a bit of confusion. It also doesn't help that there are plenty of other terms as stated above that people casually use to describe these types of projects.

Frequently I will have clients call me who ask me what the difference is between all these terms, and I would then explain the above. But now, things should be a lot simpler going forward.

Beginning last year, all of these terms have been unified - And now they're all referred to as Accessory Dwelling Units, with certain ones being qualified as Junior Accessory Dwelling Units (basically, ADUs under 500 square feet).

So, since 2020 the state of California has implemented new Accessory Dwelling Unit regulations and the cities have all begun to adopted this term. So now, whenever you hear the term Accessory Dwelling Units, that also covers granny flats, pool houses, Guest homes, or Casitas.

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