30 Most Popular ADU Questions Answered By Professionals

Nov 22, 2022 | ADU

Additional dwelling units are booming in popularity due to a variety of new incentives and laws that make it easier than ever to build one. Despite their growing popularity, many people still have a lot of questions surrounding ADU development that they need answers to before starting their project. With such a vast array of rules and regulations surrounding ADUs, it is understandable why.

There are different types of ADUs you can build with a variety of costs associated with them. Ever-changing laws in states and local governments are continually making it easier to construct your own. Read on to find out the answers to the 30 most popular ADU questions asked by people like you.

ADU Basic Facts

If you are new to the world of ADUs, you may have some questions surrounding the basics of ADU construction. From what ADUs are to the different types you can build; we can help answer these questions.


1 What Is An ADU?

An ADU, which stands for an additional dwelling unit, is a smaller residential unit built on a single or multi-family residentially zoned lot.

ADUs can be used as living or non-living spaces but must include a kitchen, bedroom, and bathroom.


2 What Are the Different Types of ADUs?

There are four main types of ADUs.

  • Attached ADUs – Shares a wall with the primary home
  • Detached ADUs – Stand-alone units
  • Garage Conversion – Converting an existing garage
  • Internal ADUs – Constructed within the existing floor plan of the primary home

There are also basement and attic ADUs, that technically fall under internal ADUs.


3 What Are JADUs?

Junior ADU (JADU), is a secondary unit no larger than 500 square feet. It is basically a smaller ADU with a few varying rules surrounding it. What makes it different from an ADU besides size is that it:

  • Can share a bathroom with the main residence
  • Either JADU or single-family residency must be owner-occupied
  • Has no parking requirements
  • Must be attached to the primary residency
  • Needs an efficiency kitchen

A few advantages to building JADUs are that you can avoid various fees and have the option to share sanitation and utilities which makes it easier to build and more affordable. A few disadvantages include that it must be less than 500 square feet and owner occupancy regulations.


4 How Big Can an ADU Be?

New 2023 ADU laws require all cities to have a height limit of at least 16 feet. If the property is within a half mile of public transit or already has a multi-family dwelling that is two stories high, the height limit must be at least 18 feet. If the ADU is attached to the primary dwelling, the height limit must be at least 25 feet or the zoning code of the property if that is lower. Cities can have higher height limitations than 16 feet, so where you live could be higher.

As a general rule, detached ADUs can be built up to 1,200 square feet. Some cities have stricter rules than this though. For example, about 150 cities and counties limit your detached ADU size based on your design plans. Generally, attached ADUs cannot exceed 50% of the square footage of the home.

Talk with your local planning board or an ADU professional to determine the ADU size limitation within your city.


5 What Are Other Names for ADUs?

ADUs go by many names.

  • Accessory apartment
  • Backhouse
  • Backyard bungalow
  • Carriage house
  • Coach house
  • Cottage
  • Garage house
  • Granny flat
  • Guesthouse
  • In-law suite
  • Laneway homes
  • Ohana (popular in the Hawaiian Islands)
  • Secondary Dwelling Unit

Although they have many nicknames, it is important to note that ADUs are not tiny homesTiny homes differ in a variety of ways from ADUs including the fact that they are mobile, illegal in most backyards, and cannot be connected to the grid unless in designated areas.


6 What Are the Benefits of Building An ADU?

There are a multitude of benefits associated with building an ADU.

  • Offers multi-generational housing opportunities
  • Income opportunity from renting the unit out
  • Helps the local community by offering affordable housing
  • House hacking opportunities
  • Increases the value of your home
  • Provides extra living or non-living space

What you do with your ADU will determine the benefits it will provide you. Overall, though, there are quite a few beneficial factors to building an additional dwelling unit.


Costs Of Building An ADU

Costs Of Building An ADU

Before beginning ADU development, it is important to have a good understanding of ADU costs. One of the biggest mistakes you can make is not properly budgeting your ADU project from the start. These questions and answers will help you understand how much money you are going to need to undergo ADU construction and how you can come up with it.


7 How Much Does Building an ADU Cost?

The type of ADU you build and your design tastes will greatly impact how much it costs to construct your ADU. On average, a new construction 499-square-foot ADU will cost you anywhere from $161,700 – $201,125. A 2-car garage conversion will cost you on average between $90,000 – 119,000.

To determine how much your ADU will cost, you can use an ADU cost calculator.


8 What Are the City Fees Associated with ADUs?

Typically, city fees are about $3,000 – $5,000 smaller ADU’s under 500 Sqf and $6,000 – $7,000 for ADU’s bigger and up to 749 Sqf. However, if your ADU is over 750 square feet, cities will add new development impact fees on you which will add thousands of dollars.


9 How Do I Finance An ADU?

There are a few ways you can go about financing an ADU. For starters, there are a variety of local government grants and loans such as the CalHFA $40K ADU grant that you can utilize to fund your ADU project. You can also finance it using:

  • Home Equity Loans and HELOCs
  • Cash-out refinancing
  • A personal line of credit
  • Construction loan
  • Renovation loan
  • Chattel loan
  • CDFI or local partnership loan program
  • Peer-to-peer lending
  • Cash savings

The best path to finance your ADU would be to apply for grants and look at government programs, and then identify the best loan that will work for your financial situation.


10 Are There Ways to Save Costs on ADUs?

Some quick cost-saving tips for you to consider include:

  • Keep your designs simple
  • Use pre-approved floor plans to expedite the permitting process
  • Buy customizable floor plans to save money on the design phase
  • Use affordable raw materials
  • Work with contractors that have established relationships with local raw material shops
  • Build a smaller unit
  • Consider doing a garage conversion if your garage is in good shape currently

Although it will save you money, never skimp on windows as they add needed natural light to make your unit look better. Also, one of the biggest ADU mistakes you can make is choosing an ADU professional based on cost only. Quality comes with a price; remember that.


11 What Is the Most Affordable ADU?

In general, garage conversions are the most affordable route for building an ADU yourself. This is because the primary structure already exists, and in some cases already have utilities and water hooked up to them.

However, there are exceptions to this statement. If your garage foundation and structure are in bad shape, it may cost more to fix them than to build an entirely new unit.


Constructing An ADU

Constructing An ADU

Constructing an ADU is a lot like constructing a house on a smaller scale. There is a lot that goes into it, and it requires a team of professionals to get it done.


12 Best Way to Find an ADU Contractor?

To find the best ADU contractor in your area, you need to start by making a checklist. The contractor you choose to work with should:

  • Specialize in ADUs
  • Be licensed and insured
  • Have a network of subcontractors
  • Have good reviews
  • Be timely and responsive
  • Be familiar with local ADU laws
  • Have a supply chain plan

Start by asking friends and family about their experience with ADU contractors. Then check reviews online from different sites like Yelp or Houzz to broaden your search. Whomever you choose should check off every box on the checklist above.


13 How Do You Build An ADU?

An ADU is usually built by an ADU contractor with a team of subcontractors in the same way a traditional wood-framed home would be built. However, there are modular (pre-fab) companies that build an ADU in a factory and then assemble it on the property. Also, you can build unique ADUs out of shipping containers and other resources.


14 How Long Does It Take to Build An ADU?

Depending on the size of your unit and how you decide to build it, a new construction ADU can take anywhere from 5 to 9 months to construct. A garage conversion can take anywhere from 3 to 4 months depending on the condition the garage is in.


15 Can I Legalize an Unpermitted ADU?

To legalize an unpermitted ADU, you will need to bring it up to code and go through a series of inspections. Various states and cities have developed unit legalization programs to make this process easier. For example, Los Angeles has the Unpermitted Dwelling Unit (UDU) Ordinance which makes legalizing ADUs easier.

To determine what you need to do to legalize your unpermitted ADU, talk with your local planning board or an ADU professional.


Uses For ADUs

Uses For ADUs

When people think about building ADUs, they usually think about using them for extra living space. However, there are several ways you can use your ADU to benefit you and your surrounding community. It is good to know about all your options before beginning construction so that you have an open mind about what your ADU can be.


16 Can ADUs Generate Rental Income?

The most common use of ADUs is for passive income generated by renting out the unit. Some people even use them for house hacking purposes to help pay off their mortgages quicker. However, if you decide to go this route, make sure you are aware of the ADU rent control factors in your city.


17 Do ADUs Help the Housing Crisis?

ADUs offer affordable housing options to low-income individuals, helping to keep them from becoming homeless. As a result, they are doing an incredible job at improving the housing crisis. Therefore, many states like California are passing laws to make ADU development easier for everyone.

The more affordable housing options there are, the lower the homelessness levels we see.


18 Do ADUs Make Good Retirement Homes?

To keep your aging loved ones out of nursing homes and assisted living, many people move them in with them. This can strain relationships and crowd homes. ADUs offer a great option to move your aging loved ones into your backyard so that you can assist them when they need help, but also allow them to maintain a level of privacy and independence.


19 Does an ADU Make a Good Guest House?

ADUs make excellent guest houses if you often have company. Your guests can maintain a level of privacy while still being close to you.

Using an ADU as a guest house is great for lodging traveling nurses, caretakers, or other personnel that often visit the home.


20 Can ADUs Be Used as Non-Living Space?

The great thing about ADUs is that they can be used for anything as long as they contain a kitchen, bathroom, and living area. Therefore, as long as you include those components, your ADU can be used as a:

  • Art studio
  • Home office
  • Man cave
  • Personal gym
  • Personal movie theater
  • Pool house
  • She shed
  • Yoga studio

The best way to use your ADU is however it will benefit you most. If that means not living in it, then go for it!


21 Can ADUs Boost Property Value?

Depending on your property and location, an ADU can improve the value of your home by 30%. Therefore, you can use an ADU to boost your property value when you decide to sell in the future.


Other ADU Questions

Other ADU Questions

There are a lot of ADU questions people have that don’t fall under the categories above. To help address some of these, we have made this “collect all” category.


22 Can You Sell an ADU Without the House?

An ADU cannot be bought or sold separately from the primary dwelling. Since it is on the same lot of land, it is considered a part of the primary dwelling’s property.


23 Can I Build an ADU And JADU?

You can build both an ADU and a JADU on your property. However, you should be aware that the JADU has an owner occupancy requirement that does not go away even if you already have an ADU on the property.


24 What Are Some of The Biggest ADU Mistakes?

Here is a quick list of some of the biggest ADU mistakes you can make.

  • Not comparing construction estimates
  • Not creating a budget
  • Not including laundry units
  • Not planning for contingency when creating your budget
  • Not planning for enough storage space
  • Skipping ADU feasibility research

For a more complete list, check our 16 biggest ADU mistakes article.


25 Do You Have ADU Appliance Recommendations?

When buying ADU appliances and furniture, also choose the options that have a dual purpose and save the most space. Here are a few options for you to consider.

  • Ductless mini-split air conditioners and heaters
  • Tankless water heaters
  • Under the counter refrigerator
  • Workstation sink
  • Washer and dryer combo
  • Sectional sleeper sofa with storage compartments

For a more complete list, check our ADU appliances and furniture article.


26 Can My ADU Have a Separate Mailbox?

If you are renting out your ADU or using it for multi-generational housing, you probably don’t want your tenants’ mail getting mixed in with yours. Luckily, most cities, like Los Angeles, can issue you a separate address for your ADU.


27 Is There a Minimum Lot Size for Building An ADU?

There is no minimum lot size required for building an ADU. As long as the plot meets ADU zoning requirements and can allow for an ADU of at least 150 square feet to be built on it, it is fine.


28 What Property Type Can I Build an ADU On?

Any residentially zoned property (single or multi-family) can have an ADU built on it. You can build an ADU on a multi-family residentially zoned plot too, as long as there is an existing primary home on the lot.


29 Is Parking Required for ADUs?

If the unit is located within a half mile from public transit, no parking is required. However, if it is not, then you will probably need to provide parking.


30 What Is the Best ADU To Build?

This is completely up to you and your circumstances. Garage conversions tend to be the most affordable and less time-consuming. However, detached ADUs allow for more creativity in design. Attached JADUs are great for multi-generational housing because you can access them from your home without having to go outside.

Therefore, the best ADU to build is different for everyone. Weigh the pros and cons of each type with an ADU professional before deciding what will be right for your needs.


Building Your Own ADU

You will probably have a lot of questions when it comes time to build your ADU. Luckily, there are several ADU professionals happy to help you build the unit of your dreams.

Here at Levi Design Build, we are a family-owned design and build company that has been developing ADUs since 1999. Our dedicated team of designers, permit expediters, and builders can help guide you through every step of ADU development.

Contact us today to see how we can help answer your ADU questions or check out our free ADU development guidebook!