How much do you really know about the different types of ADUs?
What is an ADU, really, when it comes down to your own property and lifestyle?
Which one do you prefer most? Do you know which ADUs are trending and more popular these days? For you, is privacy more important, or is lowering the price your number one goal? These are all real questions. And if you are seriously thinking about building an ADU, you should be asking them, too. Because the truth is: there are different types of accessory dwelling units out there, and each one has its own ADU construction cost, its own challenges, its own benefits. You can’t just jump into it and say, “I’ll build the cheapest one” or “I’ll go with the fanciest one.” It’s not that simple. Every ADU type can change your lifestyle, your family’s comfort, your land value, and of course, your budget. So, let’s dig into the types of ADUs together.
ADUs as Future-Proof Investments
ADUs are not just side projects. They are future-proof investments. And choosing the right type is one of the most important steps you can take. Why? Because the type of ADU you build will affect:
• Your future land value.
• Your family’s privacy and comfort.
• Your long-term income potential if you rent it out.
That’s why I say a little obsession in this stage can actually be very useful. This is the one place where overthinking pays off. Ask yourself: should I convert my basement into a cozy little unit with a lower ADU construction cost, or should I spend more and build a whole new structure in the backyard? Is it smarter to sacrifice my garage and turn it into a rental, or should I keep it as parking space? These are not easy choices, and each one comes with trade-offs. Let’s go through the different types of ADUs one by one.
1.Detached ADUs
Among all the types of ADU homes, detached ADUs are the ones that feel most like a completely separate house. They are built as independent units, usually in the backyard, and they offer the highest level of privacy for whoever lives inside as residents.
This is why they are very popular among renters. Most tenants prefer a space where they don’t hear or see the landlord every day. A detached ADU gives them that comfort.
But let’s be honest here: detached ADUs are also the most expensive ADU type to build. They need a new foundation, new utilities, full exterior construction, roofing, and landscaping. Basically, you are creating a whole new house from the ground up.
On the other hand, they add the most value to your property. So yes, you pay more, but you also get more in return. For many homeowners, a detached ADU is not just a space—it’s an investment strategy.
2.Attached ADUs
The next option is attached ADUs. These are units that share at least one wall with your main house. Sometimes they are built as extensions, sometimes they are created by converting a side space, or even by building above your garage.
The big advantage of attached ADUs is cost. They are less expensive than detached ones because they can share walls, utilities, and even parts of the foundation with the main house. You don’t have to start from zero.
And still, they have their own entrance and function as a private unit. So, they are not completely “inside” your home. They stand somewhere between independent and connected.
If you have unused storage, or extra space in your yard that can handle an expansion, an attached ADU might be the most logical choice.
3.Garage Conversion ADUs
Now let’s talk about garage conversions. Honestly, this is one of the most popular ADU types. Why? Because so many garages are simply wasted space. They become storage rooms, or worse, junk rooms. So why not turn that space into a livable unit?
Garage conversions are cheaper than building from scratch because you already have a structure: four walls, a roof, and a foundation. But don’t get me wrong — it’s not as simple as putting in a bed and a kitchen. Garages need serious upgrades to be turned into livable spaces. You’ll probably need insulation, new plumbing, electrical work, maybe even structural retrofits or roof upgrades.
The main drawback of garage conversions is obvious: you lose your garage. Which means you need to park your car outside, or build a carport. Some people don’t mind, but for others, it’s a dealbreaker.
Still, when you balance the costs and the benefits, garage conversions remain one of the smartest and most popular choices among homeowners.
4.Basement or Interior Conversion ADUs
Another option among the different types of ADUs is basement conversion or interior conversion ADUs. This simply means you take an existing part of your house — your basement or some interior area — and turn it into a livable space. Sounds easy, right? Because you already have the walls, the foundation, the roof. Everything is there.
But here is the tricky part: this type of ADU can surprise you with hidden costs you didn’t expect. Waterproofing, plumbing upgrades, electrical rewiring, or even adding egress windows — these can suddenly show up in the middle of the project. So yes, at first glance it looks like the cheapest type of ADU home, but don’t be too fast in your judgment.
Still, if you want the most cost-efficient option among all the ADU types, basement or interior conversions are definitely a winner. They can be extremely functional and useful for family purposes. You can create a private space for grown kids who want independence, or a cozy unit for in-laws or guests who need their own corner while still being close to the family.
5.Junior ADUs (JADUs)
And then we have Junior ADUs (JADUs). This is another category in the types of accessory dwelling units, but a smaller one. A JADU is usually no more than 500 sq. ft. and it’s made inside the main house itself, with its own entrance. The interesting part is that a JADU can even share a bathroom with the main house, which makes it very cost-effective compared to other ADU types.
But let’s be clear: privacy is less here. A JADU is not the same as a full detached ADU. It’s more like a small, separate space for a student, a relative, or even a low-cost rental. Very easy to build, very affordable, but limited in independence.
Cost Comparison
So, if we want to line up the types of ADUs from the most expensive to the least expensive, here’s the order:
Detached ADU > Attached ADU > Garage Conversion > Basement/Interior Conversion > JADU
Of course, this is just the general rule. Every project comes with its own details that can move the cost higher or lower.
Conclusion
What do we take from all this? The simple truth is: not all ADU types are created equal. Each one comes with its own personality, its own cost range, its pros and its cons.
If privacy and property value are your main goals, then a detached ADU is the best choice. If you want a balance between cost and independence, then attached ADUs and garage conversions make a lot of sense. And if you are really on a tight budget but still want that extra unit, basement conversions or JADUs are your winners.
At the end of the day, the types of ADUs are just tools. The right one depends on what you really need — for your family, for your land, for your income. So, take your time, think about it carefully, and don’t rush. Because once it’s built, your ADU is not just a project anymore. It becomes part of your home, your lifestyle, and your future.
So, among all these different types of ADUs, which one do you feel is yours?