Just What is an ADU Anyway?

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OK - you've made it to this website, and you see pictures of small houses all over the place - and you see "ADU' at several locations. But it's possible you might not know what an ADU is. That's ok. It's not a term that gets used in Central Pennsylvania much (yet), and it's not one that you would instantly think of to do a search on Google. Chances are, though, that you know the concept of an ADU, but you just haven't been able to put an official name (or acronym, in this case) to it.

Rest easy, my friend. This article is going to tell you exactly what an ADU is - and - you'll be ready to talk about it with your friends (no Secret Society membership needed...even though it feels like it should right now).

ADU = Accessory Dwelling Unit

ADU is an acronym for Accessory Dwelling Unit. Maybe this doesn't make it much clearer to you, because these three words are also words you don't normally think of (unless you're a building nerd like me who geeks out on this). I find it best to look at one word at a time. When you understand each one, you'll see how they fit together to explain exactly what they are.

ACCESSORY - The word itself is pretty self-explanatory. But, let's first think of it outside of housing. You get dressed for the day and put on your work clothes. That's the main outfit. You decide that you want to spiff it up a little, so you add some accessories: a tie, a purse, a wristwatch, a coonskin hat (hey - no judgment here). Although your main outfit takes care of the majority of your needs (you know...covering yourself up so you don't get arrested), the accessories just enhance and often serve additional purposes (especially those purses for the ladies who still can't figure out why dresses don't usually have pockets).

DWELLING - Again, the word itself is pretty self-explanatory. A dwelling is a place where someone lives (or works). I'm sure there's a more official definition, but I'm not one of those type of people who cites a dictionary because I can't think of my own thing to say. You get it. Enough said.

UNIT - This word simply means "an individual measurement." Yeah - I agree. This word is a little "cold." I mean - a better word could be used here, but I guess it's better than "Thing," and I didn't choose it. Some very even-more-nerdy-than-me architect-type person chose to use this word. And I think it doesn't make it any easier for the typical person to understand. But just think about it this way. It's a single little building (and why that aforementioned nerdy architect person didn't choose "building" instead of "unit" is beyond me).

Put those words together, and you have: An extra (ACCESSORY) living/working (Dwelling) building (UNIT) on your property.

To save you time and breath, you can just say "ADU". Besides, you'll sound fancy and a little less nerdy-architect-type, too.


What Can You Use an ADU For?

Accessory Dwelling Units come in many different types, and they are so versatile that there is often overlap or the ability to use them in different ways.

RESIDENTIAL: People often choose to build an ADU on their property to house extended family members nearby (but giving everybody their own private spaces). These are great for:

  • Aging parents to keep close and let them age-in-place with the support of those who know them best.
  • Young adult children still trying to get their feet on the ground but aren't quite ready to rent or buy their own house.
  • Extra space to house the extra relatives during the holidays.

COMMERCIAL: Some people look to build an ADU to give them a business space. Some examples:

  • Home Office space outside of the primary home. This gives them a way to truly separate home/work in our remote-work society.
  • Starter Office for a budding company that just can't fit in the home. I've seen these placed beside primary homes or in alleys of cities (think little bakeries, accounting office, etc.).

ADDITIONAL INCOME: Where allowed, ADU's can be great rental units (there's that word again). Savvy investors know they can build an ADU for things like:

  • Their first rental property on their own property.
  • Short-term rentals on properties near attractions (e.g. AirBnB).

Where Do ADU's Go?

An ADU - when allowed by your local Central Pennsylvania municipality - can be placed on the same lot as your main home. That's what makes it an accessory! See the picture below of an example - where a C-450 Plan ADU is being planned on a lot in Mechanicsburg, PA. You'll see the main building on the right, and the proposed ADU plan on the left.

Now - it should be known that ADU's are not permitted everywhere, In Pennsylvania, each Municipality rules itself. So, you need to do your homework by checking into your local Zoning Codes. If that feels overwhelming, that's where we can help. We're building a database of Municipalities and their Zoning Laws that lets us know where ADU's are allowed and/or what you might need to do to have one allowed on your lot. So, if we end up scheduling a free consultation to review your lot, we'll be able to review what is possible.


Other Names for ADU's

Even though you may not have heard of an Accessory Dwelling Unit before, you probably have heard of some other terms that essentially mean the same thing (without that nerdy-wordy-architecty-person getting involved). In fact, I explored many of these names when I was trying to figure out how to best explain the homes custom-built by Blue Bear Homes. In the end, ADU was what I thought should be front-and-center, but you'll see some of these words peppered in the pages.

Here are some of those other terms that might be more familiar to you:

  • Backyard Cottage (my preference - though - they're not always in the backyard).
  • Carriage House
  • Garden Cottage
  • Granny Flat/Pod
  • In-Law Home/Suite
  • Multi-Generational Home
  • Secondary Home
  • Tiny House

But - any way you name it - it's still: An extra (ACCESSORY) living/working (Dwelling) building (UNIT) on your property.


I hope this helps explain what an ADU is, and - even more - I hope it's exactly what you're looking for. When you're ready to explore how an ADU can help you out with your needs (whether that's for family or for some extra income), I'll be here!

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