Claremont ADU Resources

ADUs By the Numbers


Number of ADUs in Claremont


Number of ADUs Permitted
in Claremont in 2021


Average Permitting Costs


Minimum Size Requirement

in Square Feet

What is an ADU?

An Accessory Dwelling Unit (ADU)—also known as a granny flat, backyard home, or garage conversion—is a secondary residential unit with a kitchen and bathroom that is an accessory to the primary home. 

What is an JADU?

Junior Accessory Dwelling Units (JADUs) are allowed to be created within the walls of a proposed or existing single-family residence and
shall contain no more than 500 square feet. They may share central systems, contain a basic kitchen utilizing small plug-in appliances, may share a bathroom with the primary dwelling, all to reduce development costs. 

Reasons to Consider an ADU

People are beginning to think differently about their living space, and the demand for housing is higher than ever. In the last two years California has passed several new ADU laws which make building an ADU on your property easier than ever before. 
There are a number of advantages of building an ADU:

Want to learn more about California ADU laws?

Q: What do I need to get started building an ADU in the City of Claremont?

A: Read “Planning Your ADU” below to discover all the aspects of planning, design, financing, and permitting you’ll need to know in order to build an ADU in Claremont!

Planning Your ADU


Design is an important aspect of ADU planning, as Claremont requires they must duplicate the appearance of the main house.

Claremont has architectural guidelines which apply to ADUs. The style of your unit needs to be compatible with your existing property. Projects should be of the same style, materials, colors, and quality as used for the primary dwelling unit, although a proposed higher quality material is allowed.

Check out some free ADU floor plans from other California cities by clicking the link below. Please note these are NOT approved for Claremont, and are for informational purposes to help get you started thinking about design.

Construction Plans

You must submit construction plans in order to obtain a building permit. Required plans include:

A site plan showing all existing and proposed structures, parking (if required), and existing mature trees.

A floor plan of the proposed ADU, and the existing structure, if project is an ADU conversion.

An elevation plan that detail exterior features such as siding material, doors, windows, roofs, trim, gutters, recesses, vents and other exterior finish details.


Financing Options

There are many ways to finance your ADU. Of course, credit scores, existing debt, and your existing equity will impact your options. You will also be assessed regarding the amount of value your ADU adds to your property value, based on comparable sales in your area.

Before you approach a lending institution, is a good idea to have an estimate of the costs, a realistic timeline, and the basic information on contracting services you intend to you.

Factors such as home equity, assets, and income will also impact your options for financing your project. Present market analysis suggests that larger ADUs (about 1,200 s.f.) have an average construction cost of $225,000 in LA County. Smaller ADUs (500 s.f.) average about $110,000 to construct. 

In Claremont, prices range from about $50,000 to $200,000 depending on size and design. Below are examples of the total cost of recent ADU projects built in Claremont:

A home equity loan is a loan that allows homeowners to borrow against their home’s value, minus what is owed on the mortgage. You gain access to your home’s stored value, which includes the amount the home has appreciated in value, and how much of the mortgage you have paid off. Home equity loans typically provide a fixed amount of cash with a fixed repayment schedule, using your property as collateral.

A Home Equity Line of Credit (HELOC) is also backed by your home’s equity and use your property as collateral, but is structured as a revolving line of credit. They typically have shorter repayment terms, and charge interest only on the amount drawn from the line of credit.

Example: If your home is valued at $400,000 and your mortgage balance is at $300,000, your equity is estimated at about $100,000. A home equity loan will generally allow you to borrow about 80% to 85% of equity. If your lender allows you to borrow 80% of the equity value, your possible loan amount would be $80,000.

Cash-out refinancing replaces your mortgage with a new home loan, with a higher balance than what you currently owe on your home. The difference between what is owed on the mortgage and the home’s value, goes to the borrower. An important note is that equity must be built on the home in order to use this option.

Example: If your home is valued at $300,000 and your mortgage balance is $200,000, your equity is estimated at about $100,000. If your bank is willing to provide a new mortgage at 80% loan-to-value, then you will receive a new mortgage of $240,000. This means that you will have $40,000 of your equity to apply toward your ADU. Note that this example does not account for closing costs or other bank fees.

Cash savings is one the best ways to finance your ADU; however, most homeowners cannot completely rely on their savings. It is important to have some cash to cover upfront expenses such as design and architecture fees, as well as permitting and required testing. Homeowners should be mindful that challenges may arise, as with any building project, which could result in a loss of invested funds.

Construction loans generally pay for plans, permits and fees; labor and materials; and closing costs. If a borrower wants to build an ADU on their property and does not have sufficient equity based on the current home value, the construction loan looks at the appraised improved home value, once construction is done, instead of the current home value.

There are two main types of construction home loans. The first is a construction to permanent loan where the money borrowed to build your ADU turns into a permanent mortgage with a term of 15-30 years, with a fixed-rate or variable-rate mortgage. There are also construction only loans, where a loan is taken only during the construction of the ADU. Once completed, a permanent mortgage is taken out to pay off the construction.

Example: If your home is valued at $300,000 and your bank were willing to lend 80% loan-to-value (ltv), then your new mortgage would be $240,000. If your appraised value after improvement is $360,000 and your bank were willing to lend 80% ltv, then your new mortgage would be $288,000.

A Personal Line of Credit is often offered by Banks to borrowers with good credit scores and income. These lines are typically free to set up and can range from $10,000 – $50,000 They do not require as much documentation as a HELOC, but hold higher interest rates than a mortgage.

An option is to use cash from retirement and investment accounts, however there may be associated costs or early withdrawal penalties. Make sure that you understand the terms of your investment and retirement accounts to minimize fees and penalties, such as those associated with IRAs and 401Ks. Money can also be borrowed against a 401K, which is usually up to 50% of your vested account balance, but you should check what terms and limits apply to your plan.

Source:    City of Los Angeles, The Los Angeles County Development Authority (LACDA)


Before you start building, you will need a building permit and other approvals from the city of Claremont. The city will need detailed plans of your ADU project that must be drawn to scale. The city needs to determine if your project conforms to local zoning regulations, and needs to make sure that the design is appropriate, safe, and up to code.

Here's what Claremont requires for their ADU permit application:

Ready to get started? Click below for the city’s ADU Permit:

City Fees

As you go through the process to obtain your building permit, there are several fees required by the city of Claremont.


Select a contractor by soliciting multiple bids. Always be sure to choose a licensed contractor. ADU construction costs typically range from $50,000 to $175,000. 

Be prepared: there might be some unforeseen complications related to construction, that could cost extra. These common issues include:

Frequently Asked Questions

ADUs are accessory to proposed or existing homes. You can apply to build an ADU at the same time or after a home is constructed on your property, but you cannot build an ADU as a stand-alone project on a vacant lot or as part of a commercial building.

Yes, you can rent your ADU, depending on the term of the rental. See below regarding short-term rentals.

Claremont is currently considering regulation of short-term rentals, but currently they are NOT allowed under city ordinance.

Yes, some garages can be converted. Note that converting a structure not originally built as housing, such as a garage, will trigger requirements to comply with residential building codes (such as windows, doors and insulation). Also, you should ensure that your structure is not overly close to power lines before construction. 

Consult with the city’s Planning Division for more information by calling (909) 399-5470.

According to the Los Angeles County Assessor’s office, new construction to the existing home, including ADU, JADU and patios, pools etc. is assessed at market value upon completion. However, the existing land and structures not involved in new construction will not be included in the reassessment. The increment of value determined for the newly constructed property (ADU or JADU), will be added to the existing assessed improvement value. 


Existing Assessed Value:$220,000$300,000$520,000
Market value of ADU on completion: $100,000$100,000
New Assessed value:$220,000$400,000$620,000


For more information, visit the LA Assessor’s ADU FAQ page.

No. Prior to recent legislation, ADU laws allowed local agencies to elect whether the primary dwelling or ADU was required to be occupied by an owner. The updates to state ADU law removed the owner-occupancy allowance for newly created ADUs, effective January 1, 2020.

The new owner-occupancy exclusion is set to expire on December 31, 2024. Local agencies may not retroactively require owner occupancy for ADUs permitted between January 1, 2020, and December 31, 2024.

However, should a property have both an ADU and JADU, JADU law requires owner-occupancy of either the newly created JADU, or the single-family residence. Under this specific circumstance, a lot with an ADU would be subject to owner-occupancy requirements.
Chapter 16.333 ACCESSORY DWELLING UNITS  (Last updated Feb. 2020)

Watch Housing Claremont's ADU Q&A Session from December 2, 2021 below