What Is An ADU? An Accessory Dwelling Unit

In today’s world, the cost of housing and buildings is so expensive that most people can’t afford to buy a house for the better part of their lives. That’s why so many people are looking for cheaper alternatives.

what is an adu
Image from mightybuildings

One of these alternatives is called an ADU. If you’ve never heard of an ADU or don’t know what it is then you are not alone. The ADU is relatively new in the modern world but they just might be the next biggest housing trend. 

What Is An ADU?

An ADU is a small building that is primarily used for other purposes aside from living. Though it can be used as a bedroom as well. ADU stands for an accessory dwelling unit and is usually less than 1000sqft.

They are most often used for hobbies, guests, and add-ons for that extra room that you need yet don’t have space for in your main house. But there are more reasons to have an ADU than to not have an ADU. 

History Of The Accessory Dwelling Unit

History Of The Accessory Dwelling Unit

The first ADUs started appearing in records after World War II when an increased population in certain countries paired with the rise in poverty supplied the demand. The 1950s and 1960s probably saw the largest number of ADUs.

Between the end of the war and 1960, San Francisco alone had over 20,000 ADUs, almost all of them built illegally. Yes, illegally because this was a way to get around property taxes and codes that normally housing units couldn’t avoid. 

By the 1970s, permits were required to build ADUs in particular and laws were put in place to avoid their construction. Not many of them held up and the construction of them didn’t slow down until the 1990s. 

Today, many ADUs are built but a far higher percentage of them are up to code and follow the correct laws when building them. The use for them is also different as the original use was primarily for in-laws to stay in. 

Types Of ADU

Image from Flavin Architects

It may not seem important to learn the different types of ADU but it actually affects the codes and permits needed to use them. So let’s quickly go over the five primary types of ADU. Without further “ADU.” 

Detached ADU

These granny pods are completely detached from your home. They usually require the most permits and have the most regulations. So, build these with care and educate yourself on what you need to build them.

Attached ADU

Attached ADUs are attached to your home but usually built specifically for the purpose of an ADU. They are add-ons to your home and work just like any other add-on. They are registered as additions rather than separate ADUs.

Above Garage ADU

You can build on top of your existing garage but the steps you go through will depend on whether your garage is attached or not. To your home that is. This is a great way to save space and add a lot more room.

Garage ADU

Image from Right Arm Construction

If you have the garage space and don’t want to use it as a garage, you can transform it into an ADU. This is usually quite easy and doesn’t require as many steps as long as you are allowed to build in your area.

Basement ADU

Basement ADUs are probably your best bet if you want to get around codes and laws. Because the basement is inside of your home, you can convert it any way you like and probably won’t need a permit.

There are a few states where you have to get a permit to do any type of construction inside of your home. So check with that first. Other than that, you should be good to go and won’t pay any extra taxes for it.

Uses For An ADU

Image from Northwest Heritage Renovations

There are many uses for ADUs these days. Many more than there were in the 1960s when ADUs were so popular. You should make sure you don’t need a permit to use an ADU for any of these before you build them. 

Granny Pod

A granny pod is one of the most popular uses for ADUs. In fact, it is considered the original use. Because granny pods were used for in-laws to stay in whenever they couldn’t stay alone or wanted to be close to family. 

In some cultures, like the Amish culture, it is the standard for in-laws to stay in what is called a “dawdi haus” which is a building where parents or grandparents live. This can be seen in many, many cultures. 

Hobby Room

There is hardly a better place for a hobby room than an ADU. Having a separate area for your hobby can feel freeing and homey. Not to mention, it lets you stay organized with a place to put all of your stuff.

The hobby you have doesn’t matter. It can be sewing, crafts, sculpting, or something else entirely. The point is to create a space for you to let your creativity flow freely and uninterrupted. No distractions! 

Home Gym

Every house needs a home gym. Because there’s not much better you can do for yourself than get healthy and in shape. You can create a home gym with a small ADU and that is all you need for your workout essentials. 

You don’t have to have a full-on public gym with everything anyone could ask for. All you really need is a small area where you can have the equipment that you and you alone will use on a regular basis.

Guest House

This is another super common use for an ADU. You can use an accessory dwelling unit for your guest room. It gives guests someplace private to stay whenever they are around, even with their own kitchenette if you see fit.

Alternatively, you can use the guest house like a pool house if you have a pool. It can work as both, using it as a pool house when you don’t have any guests and a guest house when you do. That way it is always in use. 

Man Cave Or She Shed

Image from GemBuilt Construction & Remodeling

If you need a place to get away, then consider turning your ADU into a man cave or she-shed. This is perfect for any family who needs a place to getaway. It doesn’t have to belong to just one person either.

A lot of families like to use their man cave ADU as a napping house or something else for whoever wants to get away at the time. It can help you get some peace and quiet if you have different hours than everyone else. 

Game Room

An ADU is perfect for a game room. It works exceptionally well for a video game room or a VR room. If you have a larger space you can make an incredible VR room that will give you the freedom to really immerse yourself.

But even better than a VR room is a family room complete with gaming consoles, board games, and more to please the entire family. Make sure you have a family game night at least once a week for the best results.


Need a safe place for the kids to get away and have some fun? You can use a playhouse that looks any way that you want by converting an ADU into one. This can work for indoor or outdoor play in any season.

If it is extra hot, you can install an AC so they can stay cool no matter how hot it is outside. Provide a minifridge if you want to offer refreshments and cool water for them too. Make it as comfortable as possible. 

ADU Laws

Image from Mighty Buildings

ADU laws will dictate the type of ADU you can build, the size, and the purpose. These laws are usually local. You almost always need a permit to build a new ADU or buy one pre-made if you are using it for anything other than a storage building.

It is illegal to rent the building out unless you have registered it as a rental. You can get the building approved for rentals or Air BnBs but be careful about renting them out without going through the legal process. 

Check local codes and laws for best results. Contractors, realtors, and lawyers all usually know the codes and can help you with the process of getting an ADU that is legal. Don’t try going at it alone or you may end up in trouble. 

Finding ADU Housing

Finding ADU housing isn’t always easy. Because of the laws in place, it can feel like everything and everyone is working against you. But if you take all the appropriate steps, it can be the best decision of your life. 

The easiest way to find them is to get help. Find someone who knows the ins and outs of the area and everything that goes into getting permits and buildings things. You can even hire a contractor to do it all for you.

Just beware that extra taxes and such are often added to ADU. Don’t let this surprise you. Learn everything you can about ADUs before you get started to avoid any unexpected costs and to go about things the best way possible.

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