Accessory Dwelling Units: A Complete Guide For 2025

Accessory Dwelling Units are the best bet to solve the latest housing crisis

The lack of affordable housing has become a nationwide problem, and Accessory Dwelling Units or ADUs can only be an effective solution to this. 

While ADUs are generally portrayed as a new idea, you’ll be surprised to know that they’ve been around for a long time, going back to the early 1980s. 

In fact, the first accessory units or apartments came up in 1979, when the Town of Babylon in the New York City area legalized them. And this was soon followed by similar ADU laws in counties and municipalities across the country. 

However, the Accessory Dwelling Unit phenomenon lost momentum in the same decade itself, only to find a fresh lease recently. 

You see, many local laws thus far only allowed the construction of a single-family home on a property, restricting the scope for secondary units. 

Nonetheless, as states are now looking for solutions to ease a historic affordable housing crisis, ADUSs have turned out to be the front-runner. That’s because not only is an ADU home cost-efficient but also solid and reliable. 

Wondering what’s more to these accessory dwellings? 

Here’s everything you need to know about ADUs: 

What are Accessory Dwelling units? 

An Accessory Dwelling Unit also called a secondary suite or apartment, is a self-sufficient second house built on the same property as the primary home.

From home to elderly family members or young children to guest accommodation, there are many ways you can put an ADU to use. Also, if your local laws permit, you can even rent the ADU and turn it into a source of passive income. 

But there’s a catch with ADUs, which is you can’t sell the unit separately since they’re considered a part of the original property. 

When it comes to construction, there is a lot of flexibility that an ADU offers you, starting right from the location. 

Your ADU can either be integrated into the main home, share the same building, or be a detached tiny home in the backyard. 

That’s interesting, isn’t it? 

Types of ADUs

Depending on their location and construction, there can be an extensive range of ADUs. But, broadly speaking, there are six ADU categories that are widely popular across the country. 

They include: 

#1. Detached ADU

As the name suggests, a detached Accessory Dwelling Unit is a self-sufficient mini home built separately from the main home. 

Built mostly in the backyards, detached ADUs are constructed from scratch and equipped with all the amenities as the primary home.

You can think of detached accessory dwellings as backyard cottages or tiny homes. 

#2. Basement apartment 

Accessory Dwelling Units can even take the form of a self-supporting basement suite or apartment. 

However, when building one such home, you’ll have to meet certain ADU-specific criteria. For instance, like all ADU homes, your basement apartment should have an entrance separate from the main house. 

Also, having essential utilities like a kitchenette, dinette, bathroom, etc., are a prerequisite for such suites to qualify as an ADU. 

#3. Garage ADU

Simply put, a garage ADU is an independent studio home built by repurposing your main home’s garage. 

And contrary to the assumption about such studios being cramped spaces, garage ADUs are actually all-inclusive living spaces featuring innovative designs that make them quite airy. So you can expect everything from HVAC systems to running water, bath, kitchen, etc., in such homes. 

#4. Carriage house ADUs

While a carriage house ADU is also built in the garage, you’ll usually need a large-sized garage with high ceilings. 

That’s because the bigger ceiling space will allow you to build a separate floor for the ADU apartment and keep the garage as a parking space. 

#5. A home addition

An ADU can also be a home addition, which depending on the design and structure of your home, can be a pop-out from either side. 

In fact, you can even build such a secondary suite to the exact length of your main home, thus making it a fully-fledged two-storied home. 

#6. Junior ADU

A junior ADU is the most compact of all accessory units with a dwelling size not exceeding more than 500 square feet. 

Notwithstanding the size, these ADU homes have all the modern housing amenities and are apt for such properties where space is a premium. 

In fact, junior ADUs are also highly preferred by those people who’re looking for a quick office space for their business. That’s because not only does it offer physical workspace for a few people but also all the essential amenities.

Meaning if you’re looking to increase your business’s value and scale it, a junior ADU might be the perfect place to do so. 

Prefab Accessory Dwelling Units: the quickest housing solution

Unlike regular ADU homes that are built either from scratch or by repurposing a particular section of your main house, prefabricated ADUs are factory-made units. 

Prefab ADU units are by far the quickest way to build a home, as all you need to do is assemble its different parts together. And with a team of three or more people, you can do so in a few hours. 

Amazing, right? 

What are the advantages of Accessory Dwelling Units or secondary suites? 

Now that you’re acquainted with Accessory Dwelling Unit homes and also their various types, you might well think about why you should build one on your property. 

So here are some advantages of ADUs over regular backyard cottages and other home extensions projects: 

#1. They’re a cost-efficient solution to the housing crisis

The lack of affordable housing continues to make headlines across the country, with policymakers debating how to remedy the situation. And an immediate solution that more or less everyone agrees to is an increased number of ADUs. 

You see, compared to regular houses, apartments, and condos, Accessory Dwelling Units are highly cost-efficient to build. 

Take, for instance, the estimates from Home Advisor, which suggest that the average cost to build a home in Florida can be anywhere between $240,000 and $350,000. 

On the contrary, you can build a fully functional ADU home for a little over $100,000. And that means, compared to a regular house, it’s not only affordable to build an ADU but also to rent one. 

#2. You can build an ADU within hours 

Yes, that’s true. 

While it can take you months to build a conventional home with Accessory Dwelling Units, it’s just a matter of a day. That’s because fastening the various steel panels is all it takes to build an ADU. 

And that’s precisely the reason why ADUs, among other materials, were so much in demand post Hurricane Ian. 

#3. An Accessory Dwelling Unit can stand strong in extreme weather

An ADU home, in most cases, is way safer than your primary home in extreme weather conditions like storms and hurricanes. 

How, you may ask? 

Well, the answer lies in the materials used to construct these accessory units. 

For instance, most modern ADUs are built with structural insulated metal panels, which are highly impact-resistant and capable of withstanding hurricanes up to category 5. 

Sounds impressive, doesn’t it? 

#4. ADU homes are eco-friendly and energy-efficient 

Apart from the budget and solid homes they make, ADU-based secondary suites are also highly sustainable. 

In fact, most of the ADUs are built with eco-friendly building materials like recycled steel SIP panels and metal roof panels, among others. 

Also, the building materials used for ADUs are recyclable and thus have zero ecological impact even at the end of their lifespan. 

Further, sustainable building materials like steel SIP panels used to construct an ADU also have great insulating properties. Meaning, you even stand to benefit from reduced utility bills that result from lesser usage of HVAC systems. 

Are there any disadvantages of building Accessory Dwelling Units?

Yes, there are some disadvantages as well, which come naturally with an ADU. And that includes the following: 

1. ADU homes aren’t seen as separate housing units. Rather, housing laws categorize them as an extension of your existing home, thus resulting in increased property taxes. 
2. If you’re building an ADU as an additional space for your family, you should be prepared for increased utility bills too. 
3. A repurposed ADU built into spaces like the basement, garage, etc., take up important storage spaces in your home. 

What are the rules for building an ADU in Florida? 

An ADU can be, indeed, the most worthwhile home addition project in the Sunshine State. More so in the wake of more Floridian counties, municipalities, and homeowners associations voting to legalize multi-family residential properties. 

Nevertheless, the ADU rules can vary in different parts of the states, starting right from the homeowners’ associations or HOAs. 

So, to begin with, you can visit your county’s housing portal, among other relevant sources, to know whether or not they permit Accessory Dwelling Units. 

Further, you should check with your respective HOA and learn about their specific ADU rules and requirements. That’s because even if county rules allow ADU construction, HOAs still have the right to regulate such buildings in terms of their length, width, height, occupancy, usage, etc. 

The final words 

Even though Accessory Dwelling Units are being looked up for easing the housing crisis, they’re more than simply a budget housing solution. In fact, you can have an ADU with all the features of a luxury apartment or suite. 

In addition to that, impact-resistant ADUs are also a great option to shelter during hurricanes and storms. 

Not to mention, they carry an impressive return on investment (ROI) and are also an excellent way to earn a passive income. 

Looking to build one such secondary suite on your property? 

You can reach out to us!

At Eco-$mart Inc, we are a team of sustainable ADU experts, and we can build you a second home in no time.