Key Takeaway
Most California homeowners finance ADU construction using home equity — through a HELOC, home equity loan, or cash-out refinance. ADU-specific construction loans are also available through a growing number of lenders. State grant programs like the CalHFA ADU Grant have provided funds in the past, but availability varies and programs can be paused. Your best option depends on your equity position, credit profile, and tolerance for variable-rate products.
What Lenders Look At
Before comparing loan products, it helps to understand what a lender is evaluating when you apply for ADU financing. The four main factors:
Home equity: Most home equity products require you to retain at least 20% equity after the loan is funded. Your usable equity is roughly your home's current value minus your mortgage balance, minus the 20% cushion lenders require.
Credit score: Most home equity loans and HELOCs require a minimum credit score, typically 620 or higher. Better rates are generally available for scores above 720. Pull your credit report before applying so there are no surprises.
Debt-to-income ratio (DTI): Lenders assess whether your existing monthly obligations — mortgage, car payments, other debts — leave room for a new loan payment. Lower DTI improves your options and rate.
Projected post-ADU value: Some ADU-specific lenders use an 'as completed' appraisal when underwriting, factoring in the home's estimated value once the ADU is built. This can meaningfully increase how much you are eligible to borrow.
Qualification criteria and loan terms vary by lender and shift with market conditions. Work with a licensed mortgage professional to understand your specific situation before committing to a financing path.
Home Equity Financing: The Most Common Path
For most California homeowners, home equity is the most accessible source of ADU funding. Three main products draw on home equity:
HELOC (Home Equity Line of Credit)
A HELOC works like a credit card secured by your home. You are approved for a maximum credit limit and draw funds as needed during a draw period, typically 5 to 10 years. You pay interest only on what you borrow during the draw period, then repay the principal over a repayment period.
How HELOCs apply to ADU projects
Interest rates are variable, tied to the prime rate plus a margin set by the lender
Funds can be drawn in stages, which matches the pace of a construction project well
You pay interest only on what you draw during construction, not the full credit line
If rates rise materially during your draw period, your payment obligations increase — this is the main risk
HELOCs work well for homeowners with significant equity who prefer a flexible draw structure and can manage variable rate risk.
Home Equity Loan
A home equity loan (sometimes called a second mortgage) provides a lump sum at a fixed interest rate, repaid over a set term — typically 10 to 20 years. Unlike a HELOC, the rate and payment are fixed from the start.
How home equity loans apply to ADU projects
Good for homeowners who want rate certainty for the life of the loan
Less flexible than a HELOC — the full amount is disbursed upfront, and you pay interest on all of it immediately
Typically carries a higher initial monthly payment than a HELOC draw period, but no variable rate risk
Works well when you have a clear, finalized project budget
Cash-Out Refinance
A cash-out refinance replaces your existing first mortgage with a new, larger mortgage. The difference between the old and new loan balance is paid to you in cash, which you can use for ADU construction.
When a cash-out refi makes sense for ADUs
Your current mortgage rate is higher than available refinance rates (less common in a rising-rate environment)
You want to consolidate existing debt into a single payment alongside the ADU funds
Your home has appreciated significantly since purchase and you have substantial equity
Note: closing costs for a refinance are typically higher than for a HELOC or home equity loan, and the transaction resets your mortgage term
Note: ADU financing decisions involve long-term obligations secured by your home. Interest rates, loan terms, and eligibility requirements are market-dependent and vary by lender. Consult a licensed mortgage professional before choosing a home equity product.
ADU Construction Loans
A construction loan is short-term financing that disburses funds in stages as construction progresses, based on completed milestones. Once construction finishes, the loan is either paid off or converts to a standard mortgage.
Historically, ADU projects fell outside conventional loan guidelines, which made construction financing difficult. That has changed as ADU construction became more mainstream. A growing number of lenders now offer products specifically designed for residential ADU projects.
Construction-to-permanent loan
This loan converts to a traditional mortgage when the project is complete. During construction you pay interest only, then begin regular mortgage payments after conversion. It avoids closing costs on two separate transactions. Best for homeowners who want a single loan that handles both phases.
Construction-only loan
Short-term financing for the build phase alone, typically 12 months. When construction is done, you pay off the construction loan with a separate product — often a HELOC, home equity loan, or refinance. Requires two closings but gives more flexibility to shop for a permanent loan separately.
ADU-specific lenders
Some lenders specialize in ADU construction and underwrite based on projected post-construction appraised value rather than current equity alone. This can improve borrowing capacity for homeowners who have less equity today but whose property will be worth significantly more with an ADU completed.
Getting an accurate project cost estimate from a qualified ADU contractor before applying for a construction loan speeds up the approval process and reduces the chance of a funding gap mid-project. Read the San Diego ADU cost guide to understand the typical cost components before you speak with a lender.
The CalHFA ADU Grant
The California Housing Finance Agency (CalHFA) created a Pre-Development ADU Grant to help income-eligible homeowners cover early project costs — design fees, engineering, permits, and site assessments. When active, the grant provided up to $40,000 per homeowner as a non-repayable award.
Current status (as of June 2026): The CalHFA ADU Grant is paused. No new applications are being accepted, and no confirmed restart date has been announced. Homeowners should check calhfa.ca.gov directly for current status. The program restarts when new state funding is appropriated.
Key things to know about the grant when it is active:
Covers pre-development costs only — not construction labor or materials
Requires the property to be the homeowner's primary residence
Income eligibility is tied to area median income (AMI) limits that vary by county
Recipients must use CalHFA-approved lenders and professionals
The grant does not need to be repaid, but misuse can trigger recapture provisions
San Diego-Specific ADU Financing Programs
Homeowners in the City of San Diego have access to ADU-specific programs through the San Diego Housing Commission (SDHC), which administers several affordable housing programs at the local level.
SDHC ADU Financing Program
The SDHC has offered low-interest loans to income-eligible homeowners to build ADUs that are rented at affordable rates. These are structured as deferred-payment loans or low-interest long-term loans, depending on available funding.
What to know before applying
Affordable-rent requirement: SDHC ADU loans typically require homeowners to rent the completed ADU at below-market rates for a specified period — often 10 to 15 years. This is often called an affordability covenant.
Income eligibility: Homeowner income must fall within specified AMI limits. Eligibility requirements and income thresholds are updated annually.
Primary residence requirement: The property must be the homeowner's primary residence.
Appropriate use case: This program works well for homeowners whose primary goal is family housing or who meet income requirements and can accept below-market rents in exchange for favorable loan terms. Homeowners seeking market-rate rental income may find the rent restriction requirements don't align with their goals.
Note: Program availability, eligibility requirements, and loan terms for both CalHFA and SDHC programs change with funding cycles. Verify current status directly with each agency before building your project budget around program availability.
San Diego also operates an ADU Bonus Program that allows homeowners to build additional units beyond standard limits in exchange for providing affordable housing. Read the San Diego ADU Bonus Program guide to understand how density incentives and affordability programs intersect.
Personal Loans and Other Approaches
Personal loans (unsecured loans from banks, credit unions, or online lenders) are occasionally used for smaller ADU-related costs — pre-construction expenses not covered by a grant, or a funding gap at the end of a project where the remaining amount is manageable.
Personal loan rates are typically much higher than home equity products because they are unsecured. For most ADU projects, which run well over $100,000, personal loans are not a practical primary financing source.
Other approaches homeowners use
Combining a smaller HELOC with a CalHFA or SDHC grant to reduce the total borrowed amount
Phased construction, where initial work is funded from savings and construction loans cover later phases
Family loans or gifted down payments on a construction-to-permanent loan (lender policies vary)
Owner-builder arrangements for homeowners with construction experience (permits and liability considerations apply)
How to Choose the Right Financing Approach
The right financing path depends on your equity, credit profile, income, and willingness to accept variable rate risk. A few patterns apply to most San Diego homeowners:
| If your situation is... | Consider... |
|---|---|
| Strong equity (40%+), stable income, comfortable with variable rate | HELOC — flexible draws match construction pace |
| Strong equity, prefer predictable payments | Home equity loan — fixed rate, fixed term |
| Current mortgage rate is above today's rates | Cash-out refinance — consolidate and lower rate |
| Limited equity today, but high projected post-ADU value | ADU-specific construction lender — as-completed underwriting |
| Income-eligible, willing to rent at affordable rates (San Diego) | SDHC ADU loan — lower interest, longer term |
| Planning phase costs only (when program is active) | CalHFA ADU Grant — up to $40,000 non-repayable for pre-development |
Before You Apply: A Pre-Financing Checklist
Sorting Out Financing Early
Financing is one of the last things many homeowners sort out and one of the first things they should. How you fund your ADU affects your monthly payment, how long the project takes to pay for itself, and whether the project makes financial sense for your specific property at this point in time.
Start with your equity position. Get a realistic project cost estimate from a licensed professional. Talk with at least two or three lenders before committing to a product. The time spent comparing options at the beginning can meaningfully change the long-term economics of the project.
If you are still in the early stages and comparing project types, the San Diego ADU permit guide covers the approval process and the San Diego ADU cost guide breaks down typical costs by project type.
Ready to talk with builders? Compare local San Diego ADU builders who can give you project cost estimates before you approach a lender, or get matched with ADU professionals for your specific property and project goals.
Frequently Asked Questions
What is the best way to finance an ADU in California?+
Is the CalHFA ADU Grant still available?+
Can I use a HELOC to pay for ADU construction?+
What is a construction-to-permanent loan?+
Does San Diego have ADU-specific loan programs?+
How much equity do I need to finance an ADU?+
Disclaimer: This article is for informational purposes only and does not constitute financial, mortgage, legal, or tax advice. Loan products, interest rates, eligibility requirements, and grant programs change frequently and vary by lender, applicant profile, and program funding status. Consult a licensed mortgage professional, financial advisor, or HUD-approved housing counselor before making financing decisions for your ADU project.
Sources and Official Resources
- •California Housing Finance Agency (CalHFA) — ADU Grant Program — CalHFA. calhfa.ca.gov — Check under 'ADU Grant Program' for current status. Last accessed June 2026. Verify current status before relying on program availability.
- •San Diego Housing Commission — ADU Programs — SDHC. sdhc.org — Check under 'Affordable Housing Programs' for current ADU loan availability. Last accessed June 2026. Verify current status before relying on program availability.
- •Consumer Financial Protection Bureau — Home Equity Loans and Lines of Credit — CFPB. consumerfinance.gov/ask-cfpb/what-is-a-home-equity-line-of-credit-heloc. Last accessed June 2026. Verify current status before relying on program availability.
- •California Department of Housing and Community Development — ADU Handbook — California HCD. hcd.ca.gov/policy-research/accessory-dwelling-units. Last accessed June 2026. Verify current status before relying on program availability.
- •HUD-Approved Housing Counselors (for financing guidance) — U.S. Department of Housing and Urban Development. hud.gov/i_want_to/talk_to_a_housing_counselor. Last accessed June 2026. Verify current status before relying on program availability.
This guide draws on publicly available information from state agencies, federal consumer protection resources, and the San Diego Housing Commission current as of June 2026. Financing programs, grant availability, and loan terms change frequently. Always verify requirements directly with the applicable lender or agency.