You have likely spent the last several months browsing floor plans, pinning interior design inspiration, and perhaps even sketching out where your new Accessory Dwelling Unit (ADU) will sit on your property. You've made the decision to build — a decision that promises to increase your property value, provide housing for a loved one, or generate significant monthly rental income. But now comes the most critical hurdle: paying for it. In the Los Angeles market, where GatherADU has completed over 127 projects, we see homeowners encounter the same crossroads every single week. The two most common financing paths for ADUs are Home Equity Lines of Credit (HELOCs) and construction loans. These two products work in fundamentally different ways, and choosing the wrong one for your specific financial profile can cost you upwards of $15,000 in unnecessary interest or, worse, leave you scrambling for cash in the middle of your build when a contractor hits a milestone and the bank refuses to release funds.
How a HELOC Works for ADU Projects
A Home Equity Line of Credit is essentially a revolving credit line secured by the equity in your primary residence. Think of it as a credit card with a very high limit and a much lower interest rate, backed by your home. For an ADU project, a HELOC is often the first thing homeowners consider because of its perceived simplicity.
In the current 2026 economic landscape, we are seeing HELOC rates hover between 7.5% and 9.5%, depending on your credit score and your combined loan-to-value (CLTV) ratio. One of the primary draws of the HELOC is the "draw period," which typically lasts 10 years. During this time, you are only required to make interest-only payments on the amount you have actually spent. If you have a $250,000 credit line but have only paid your contractor $50,000 for the foundation, you only owe interest on that $50,000.
The defining feature of a HELOC for ADU construction is control. There is no bank-mandated "draw schedule." You do not need to wait for a bank inspector to walk the site before you can pay your plumber. You simply write the check. For projects ranging from $100,000 to $500,000, this flexibility is a massive advantage for homeowners who have a high degree of trust in their builder.
How a Construction Loan Works for ADU Projects
A construction loan is a short-term, specialized financial product designed specifically for the act of building. Unlike a HELOC, which looks at the value your home has today, many ADU construction loans look at the value your home will have after the ADU is completed. This is a game-changer for homeowners who don't have $300,000 in sitting equity.
These loans are typically structured for a 12-to-18-month term. The lender releases funds in "draws" tied to construction milestones:
- Stage 1: Deposit and Permitting
- Stage 2: Foundation and Under-slab Plumbing
- Stage 3: Framing, Roofing, and Exterior Sheathing
- Stage 4: Rough-ins (Electrical, HVAC, Plumbing) and Insulation
- Stage 5: Drywall, Paint, and Interior Finishes
- Stage 6: Final Retainage and Certificate of Occupancy
Interest rates for construction loans are usually slightly higher — currently ranging from 8% to 11%. The bank sends an inspector at each milestone to verify the work before releasing the next chunk. Once the build is finished, the loan usually "converts" into a permanent 30-year mortgage, or you pay it off by refinancing.
Head-to-Head Comparison
| Feature | HELOC | Construction Loan |
|---|---|---|
| Current Rates (2026) | 7.5% – 9.5% (Variable) | 8% – 11% (Fixed or Variable) |
| Loan Basis | Current Equity Only | Projected "As-Completed" Value |
| Draw Structure | Borrower-controlled (Revolving) | Lender-controlled (Milestones) |
| Flexibility | High — Pay anyone, anytime | Low — Requires inspections/approvals |
| Closing Costs | Low ($0 – $2,000) | High (2% – 5% of loan amount) |
| Approval Time | 2 – 4 Weeks | 45 – 90 Days |
| Best For | High-equity homeowners, projects under $200K | Major builds with low current equity |
The Real Cost Difference: A $250,000 ADU Example
Let's look at a 9-month build costing $250,000. We assume the homeowner draws money linearly ($27,777 per month). Comparing a HELOC at 8.5% against a Construction Loan at 9.5%:
Month 1: Draw $27,777. HELOC Interest: $196.75. Construction Loan Interest: $219.90.
Month 5 (Mid-point): Drawn $138,885. HELOC Interest: $983.77. Construction Loan Interest: $1,099.50.
Month 9 (Final): Full $250,000 drawn. HELOC Interest: $1,770.83. Construction Loan Interest: $1,979.16.
Over 9 months, total interest on the HELOC: approximately $8,854. On the Construction Loan: approximately $9,895. The HELOC saves about $1,041 in interest. However, the construction loan carries $5,000 to $10,000 more in closing costs. For a $250,000 project, the HELOC is almost always cheaper if you have the equity. The construction loan's value is in borrowing against the future value of the ADU.
Want help choosing the right financing? Schedule a free consultation or call (323) 591-3717.
When a HELOC is Better
- You have significant equity: Most lenders allow a CLTV up to 80-85%. If your home is worth $1.2M and you owe $400K, you have plenty of room for a $250K HELOC.
- Your project is under $200,000: The high closing costs of a construction loan don't make sense for smaller projects.
- You want speed: HELOCs close in weeks. Construction loans take 45-90 days.
- You want control: No bank inspector required at each milestone. You pay contractors directly.
When a Construction Loan is Better
- You are "Equity Poor" but "Income Rich": You bought recently with a small down payment. The construction loan borrows against your home's future value with the ADU.
- You are building a $300,000+ ADU: The "as-completed" valuation gives you massive borrowing power your current equity can't match.
- You need accountability: The bank inspector verifies work before releasing funds, protecting you from overpaying for uncompleted work.
- You want to consolidate: Roll your existing mortgage and construction costs into one new 30-year fixed loan at the end.
The Third Option: Cash-Out Refinance
A cash-out refinance replaces your existing mortgage with a new, larger mortgage and gives you the difference in cash. This was the "gold standard" when rates were at 3%. In 2026, it's harder to swallow if you're sitting on a low fixed rate. However, if your current rate is already high, or if you need over $400K and want the security of a 30-year fixed from day one, the cash-out refi provides a lump sum that lets you act as a "cash buyer" with your contractor — which can lead to discounts.
CalHFA ADU Grant Program
For California residents, the CalHFA ADU Grant provides up to $40,000 in forgivable funds to reimburse "pre-development costs" — architectural designs, permits, soil tests, and impact fees. The grant can be paired with both HELOCs and construction loans. Many of our clients use a HELOC to fund the start, then apply the $40,000 grant to pay down the HELOC balance immediately. It effectively turns a $250,000 loan into a $210,000 loan.
Fannie Mae HomeStyle Renovation Loan
This is becoming the "holy grail" of ADU financing. Fannie Mae allows the lender to use projected rental income from the ADU you haven't even built yet to help you qualify. If your Debt-to-Income ratio is too high for a $250,000 loan, the appraiser can add a portion of the projected $2,800/month ADU rent to your qualifying income. This has allowed dozens of GatherADU clients to get approved when a standard HELOC would have been denied.
What Lenders Look For
- Credit Score: 680 is the floor for most, but 740+ gets the best rates.
- DTI Ratio: Total debt payments should be below 43-45% of gross income.
- Detailed Construction Contract: A fixed-price contract with detailed Scope of Work from a licensed contractor.
- Permit Status: Most construction loans won't close until permits are "Ready to Issue."
- Contractor Vetting: The bank checks the contractor's license, insurance, and references.
Frequently Asked Questions
Can I pay the HELOC interest using ADU rental income?
Absolutely. If your $250,000 HELOC costs $1,700/month in interest and you rent the ADU for $3,000/month, the ADU is self-funding and putting $1,300 of profit in your pocket while paying for its own debt.
Is the interest on an ADU loan tax-deductible?
Generally yes, if the loan is used to "buy, build, or substantially improve" the home that secures the loan. Always consult with your CPA on specific deductibility rules post-2018 tax reform.
What happens if costs go over budget?
With a HELOC, you can draw more money (assuming you have the limit). With a construction loan, you're usually locked into the original amount. Always include a 10% contingency in your initial loan request.
Can I get a construction loan if I already have a first mortgage?
Yes. This is called a "second lien construction loan." Several of our partner lenders offer it, allowing you to keep your first mortgage (and its low rate) while adding a second loan specifically for construction.
How does the appraisal process differ?
A HELOC appraiser looks at what homes with ADUs have recently sold for. A construction loan appraiser looks at your specific plans and estimates what your house will be worth when the ADU is finished. The latter usually results in a higher valuation.
Do I need to tell my current mortgage holder I'm building an ADU?
If you're getting a new loan (HELOC or construction), that lender will know. You do not typically need "permission" from your primary mortgage holder, as building an ADU is a property improvement that increases their collateral value.
Ready to explore your options? Schedule a free financing consultation or call (323) 591-3717.
Written by Argi Avetisyan, Co-founder and CEO of GatherADU. 127+ ADUs completed across Los Angeles County.
