How to Build an ADU – The Complete Guide

Adding an extra dwelling unit to your house is an excellent way to increase your living space. Auxiliary apartments are inexpensive housing for independent living geared towards older adults 55 and over, with one apartment having two bedrooms. These are connected to the side of a single-family home. In certain circumstances, a full kitchen and bathroom are possible. Before undertaking any development, make sure you know the local building codes. A professional can help you establish an ADU housing plan and track its success.

What is an ADU (Accessory Dwelling Unit)?

How to Build an ADU- The Complete Guide

Additional homes or apartments, with legislative and regulatory terms, erected on the same property as a primary residence are known as Accessory Dwelling Units (ADU). Although the apartment cannot be owned or sold on their own, they are often used to create additional income via renting or housing a close relative.

As a starting point, consider the following for an ADU Unit:

  • An ADU housing or accessory dwelling unit is a second residence erected on the same site as the primary residence.
  • Depending on your needs, an ADU might range from a rental cottage for short vacations to a multi-level detached garage with a separate apartment above it.
  • ADUs are subject to a wide range of zoning restrictions and laws, depending on where you live.
  • Supplementing your income with a rental from an ADU may be an option for you.
  • Your monthly utility bills will increase if you install a separate dwelling unit (ADU).

While the benefits of ADU houses are numerous, many people are skeptical about their legality. ADUs are not permitted in every city, but California has passed new laws that have increased their acceptance. They can be used for several purposes, including a private retreat or a workplace.

Things to Consider Before Building an ADU

You may be thinking: “Can I build an ADU on my property?”

Building an ADU requires rigorous planning. You should consider the following:

  • Money. Building an ADU to boost property value is amongst the most prevalent reasons householders do so. The cost may be little compared to the extra value it adds to the home. Building an ADU may be worthwhile to consider if you are selling a property but not getting great offers. It may attract a whole new set of buyers. They may be ready to pay a fair premium if the ADU revenue would help them pay down their mortgages. Likewise, renting out a section of your house may be a better option than renting out the whole property.
  • Fire restrictions. The same varies from state to state, so understand where you live. You may need to make further changes to your small dwelling units to fulfill local construction codes. Like every housing unit, an ADU house should be fire-resistant and have an accessible exit.
  • Local property development restrictions. You must keep these in mind while building an ADU. This factor will determine the maximum number of units you may construct and their full height. Depending on how near the structure is to the utility lines, you may also need to set it back. When in doubt regarding your city’s codes, contact the planning department. You’ll need to research the property development requirements to determine how much space you have available for an ADU living space.
  • Permits and inspections. Before beginning your project, find out what permits and inspections your local regulatory body requires. This might be an expensive venture. Therefore, it’s critical to be well prepared and knowledgeable of all local norms and regulations. If you want help, you could also consider contacting a local contractor.
  • Land issues. You will need to address any land issues that may arise in your ADU designs. It is critical that the ADU housing is car-accessible and does not need a separate entrance or stairs. Ensure that the ADU is easily accessible otherwise and can be maintained. When planning an ADU, create a private kitchenette, lounge area, and bedroom for visitors to minimize interruption.

What are the permits required for building an ADU?

How to Build an ADU- The Complete Guide

ADUs exist in a broad range of forms and sizes, with varying degrees of regulation in different areas. If you’re unsure where to begin, you can always seek guidance from the city’s planning office. Several towns require that a permitted ADU be at least four feet away from a principal dwelling to be authorized.

In California, the minimum setback distance is three feet. In contrast, you may apply for an ADU housing permit if you currently have a garage you wish to transform into your ADU.

Obtaining an ADU permit is the first step in constructing an ADU on your property. The height, characteristics, and other restrictions of the ADU building permit will be mentioned in the license. To avoid being rejected, you must be aware of these constraints before beginning your project. The first step in starting your project is to get acquainted with the local legislation.

All Other Permits

You may need extra approvals for your ADU or senior flat, depending on where you want to build it and what you want to make there. Wondering how to get an ADU permit? Here are a few factors you need to consider:

  • Location/site

The next step in constructing an ADU is getting a site permit. Many towns and states demand these permissions before doing any project in a particular place. It is critical to understand these principles before constructing a new structure in a new location. Before you begin, seek further information from the city’s building department. A zoning permit is usually necessary for every residential building project.

  • Site-specific situations

There are a few things you should know if you’ve always wanted to construct an ADU on your property. The first thing to examine is the unique characteristics of your location. For example, if it is slanted, it will need to be leveled or supported below. If you want to install an ADU for an older adult who may have mobility challenges, you should think about how they will enter the room.

  • Non-conforming ADUs

Before an ADU may be erected in California, you must first get a construction permit. If you’re considering building an ADU for your house, you should be aware of the regulations that apply to this sort of auxiliary construction, like permits to construct a modest standalone dwelling up to 800 sq. ft. and no more than 16 feet in height. Construction permits for ADUs under 16 feet tall and 750 sq. ft. cannot be denied. Built inside a house or outbuilding, an ADU may be as tall as the present framework.

  • Applications for address allocation

If you want to construct an ADU, you must also get permission. This permit will outline the limitations and the ADU’s height and feature limits. Make sure to familiarize yourself with the laws and regulations in your city and municipality, or you may be refused construction permission entirely. Furthermore, you’ll need to secure a home equity loan before starting building, or your lender may require you to have a loan pre-approved.

Costs involved in building an ADU

How to Build an ADU- The Complete Guide

The cost of constructing an ADU varies with the size of the facility. However, the process may be relatively complex and requires a great deal of inventiveness in design and planning. Building code compliance, landscaping, and expert aid may be extra expenditures. Given the ADU unit cost complexities and spending involved, employing an expert to assist you is a wise decision. There are also several resources accessible to help you with the building process.

Before you begin construction on an ADU, you should determine what kind of costs will be incurred. The land is the most expensive component. The ADU cost is determined by its location and the number of bedrooms. If you want to use the ADU property for commercial purposes, you can combine the utilities and water and sewage connections.

Site preparation, grading, and demolition are examples of complex expenses. These are generally between 8% and 15% of the overall project cost and additional residential costs levied by the contractors or construction managers. Before you begin building, you must confirm these costs.

How to Build an ADU?

A general question might be coming to your mind: “Can I build an ADU on my property?” The answer is not too complicated. If you want to learn how to build a house with an ADU, you must first determine if you are up to the challenge. If you are uncertain about the design, you may get an architect’s design and engage a drafting technician for advice on how to build an ADU.

You’ll need to think about financing, design approval, electrical work, plumbing, and landscaping. These are the steps to understanding the different ways an ADU building can be constructed:

1. Design the ADU (get help from professionals).

How to Build an ADU- The Complete Guide

It’s a good idea to speak with pros when designing an ADU to avoid making expensive blunders. While there are fewer rules for ADU housing than traditional single-family houses, these structures are sophisticated and must be built correctly. To ensure the appropriate construction of your ADU, it is essential to follow a tried-and-tested method. Hiring professionals is an excellent way to avoid hazards like squandering money on supplies, having contractors mess up, and not acquiring a construction permit.

2. Get a Loan Pre-approval.

Get a loan pre-approval before you start designing. A lender will look at your current financial status to decide how much you may borrow. Bring your ideas and proposals with you to begin the pre-approval process. A pre-approval will simplify the procedure and ensure that the project can be adequately funded up to a certain amount.

3. Get the Design Approved by Local Authorities.

It is essential to get consent from local authorities before beginning construction on an ADU. You may contact a contractor and start the job after you’ve been authorized. It is essential to get the design approved by local authorities before beginning the project. Design approval is a crucial part of the process since the government may make revisions to your plans if you do not have the required permissions and blueprints.

4. Sort your Finances.

There are many critical stages in designing and developing a budget to build an ADU. The reason you shouldn’t apply for a loan right away once it’s been pre-approved is that the local authorities may want adjustments to the original ADU design plans before they accept it. If you haven’t planned for these adjustments, they might cost you.

5. Get Bids from Contractors and Choose One.

Before you choose a contractor, you should collect all of the offers for the ADU from potential builders. The job will be priced differently by each contractor. It is vital to choose someone who will communicate well with you, solving the primary query, “How much does it cost to build an ADU?” After you’ve decided on a contractor, you’ll need to set a budget. Many homeowners, however, choose to apply for construction refinancing to include the cost to convert the garage to ADU.

Which Type of ADU Should I Choose?

It is not only vital to examine the design of the ADU structure itself, but it may also be a time-consuming procedure. While no prior building expertise is required, it is crucial to understand how ADU plans vary.

Before choosing the types of ADU to construct, consider the following:

  • Budget: The first thing to think about is your budget. If the cost of an ADU is less than $200,000, a prefabricated design is an excellent option. You will save money on the expense of constructing ADUs. You’ll also have fewer difficulties since a prefab model is usually completed in six to nine months. Still, secondary units like stick-built backyard ADUs might take up to a year.
  • Building size: The size of the building is the second consideration. An attached ADU in California is usually larger than a prefab ADU. This distinction may have an impact on how you charge renters. A separate entrance, for example, will increase the ADU housing unit’s appeal to renters.

What is the California ADU Program and its Benefits?

An ADU home is a widely used phrase that refers to additional dwellings or apartments on the same property. Granny flats, in-law apartments, and backyard cottages are other names for ADUs. The California Department of Housing and Community Development normally permits building a single ADU of 1,200 sq. ft. An ADU is a residential construction that incorporates permanent accommodations for living, sleeping, cooking, eating, and sanitation on the same plot as the single-family residence.

  • ADU Programs in California

The California ADU Program is a state-sponsored program that encourages homeowners to construct a second unit on their property. The concept is intended to maximize urban space by promoting the conversion of garages into dwelling quarters. In California, there are already five ADU-related statutes in the books, with several of them aiming to simplify the process for homeowners.

  • Reduces building costs

Whether you want to create an ADU as an addition to your current house or a free-standing construction, it is critical to choose the best building technique for your needs. The most costly alternative is a free-standing ADU, which requires permits, excavation, and landscaping. Prefab construction may save you money, but be sure you adhere to local building requirements.

  • Upgrades value of the property

Many individuals are unaware that adding a housing unit to a property may boost its value. The new rule permits anyone to add an ADU to their house, each with an entrance and tax responsibility. These extra apartments may be inside, connected, or separate. This law may assist you in building the other house you have been dreaming of, whether you are seeking a means to repay the project’s cost or not, as per the ADU cost calculator.

  • Respects the confidentiality of residents

In California, new state legislation to preserve the privacy of persons who live in auxiliary dwelling units (ADUs) has been proposed.


Individuals and communities utilize ADUs in diverse ways. Renting an ADU space near work would help individuals save money by shortening daily commutes. These savings can ultimately help boost a person’s retirement savings! The correct technical skills can help you satisfy all regulatory standards while also adding value to your house. Do you have questions concerning ADUs? At Design Everest, we offer a list of competent California engineers eager to help you. Contact us today!

ADUs (sometimes known as secondary dwellings) are compact, attached or detached homes located on the same property as the primary residence. Pre-approved
Accessory dwelling units, or ADUs, are additional living spaces that can be installed on your property. An ADU can be converted from existing facilities
ADUs, or accessory dwelling units, are extra living spaces that can be built on your property. Depending on the available area and the clients' needs,
So many California regulators are providing additional guidance and assistance for homeowners to expand on their properties. Palo Alto is a Bay Area


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