The right answer when HELOC and cash-out refi can't fund the project
Construction Loans for an ADU in California: 2026 Rates, Mechanics, and When They Beat HELOC
A construction loan funds an ADU project through staged disbursements tied to inspection-recorded construction milestones, then converts to a permanent mortgage when the project completes. For California homeowners who bought their main home recently and don't have $200K+ in home equity, construction loans (or "construction-to-perm" loans) are often the only financing path that funds a full new detached ADU build. Rates run higher than HELOC during construction (typically 8.0%–10.0% in May 2026, sometimes as low as ~7% with credit unions), but the staged disbursement structure is a natural fit for ADU construction milestones, and the conversion to permanent mortgage at completion gives you the fixed-rate stability HELOC lacks. ADUscale is not a lender, mortgage broker, or financial advisor; we do not originate loans or provide investment advice.
8.0%–10.0% construction rate~6.50% perm rate5–7 inspection drawsACV-based underwriting
ACV-based underwriting unlocks financing for low-equity homeowners.
Section 02
Who's Reading This
The four California ADU sub-profiles relate to construction loans very differently:
Profile A · post-2022 buyer
The Recent Mover
The page's primary reader. Has $80K–$180K of equity, not enough to fund a full $300K detached build with HELOC. Construction loans use after-construction value, which is what unlocks financing capacity for this profile.
Posture: Construction loan is often the only path that pencils.
Profile B · any age
The First-Timer
Has never financed a construction project. The 5–7-draw inspection-anchored structure is initially intimidating; the honest framing here is that the structure is what protects the homeowner, not what burdens them.
Posture: The draw structure is a feature, not a bug.
Profile C · 40–55
The Equity Optimizer
Rarely needs a construction loan. With $400K+ of equity, HELOC is structurally cheaper. The page tells them so directly so they don't get sold a construction loan they don't need.
Posture: HELOC is structurally cheaper at this equity position.
Profile D · 55–65
The Aging-In-Place Planner
Typically not a fit. Construction loans introduce variable-rate construction-phase debt and a perm-conversion event, both of which add complexity that this profile shouldn't take on close to retirement.
Posture: HELOC, refi to fixed perm before construction, or wait.
Section 03
Two Types — Construction-to-Perm vs. Renovation Loan
Type 01 · For new detached construction
Construction-to-Permanent (CTP) Loan
A single closing covers two phases: 12 months of construction at one rate, then automatic conversion to a 30-year permanent mortgage at completion.
Phase 1 · Construction (~12 months)
Loan funds in staged draws tied to inspection milestones
Interest-only payments on drawn balance
Construction-phase rate: 8.0%–10.0% (some CA credit unions ~7.0%)
Pay only on what's been drawn, not the full approved loan
Phase 2 · Permanent (30-yr fixed)
At final inspection, loan automatically converts to perm
Permanent rate locked at construction loan closing (60–120 days)
Single monthly principal + interest payment
Often replaces existing mortgage (lock-in trap to watch)
Final inspection passed + Certificate of Occupancy
10–15%
07
Retention
Punch list complete + final lien releases
5%
The lender sends an inspector (often the same building department inspector who's already verifying the work) to confirm each milestone before releasing the next draw. The structural similarity to Verified Milestone Payouts means construction loans pair naturally with our payment-protection framework.
Section 05
Current May 2026 Construction Loan Rates + Terms
Rate sheets verified against Federal Reserve H.15 for the perm-phase 30-year fixed reference (currently around 6.50%).
LENDER TYPE
CONSTRUCTION RATE
PERM RATE
TERM
DOWN / EQUITY
National bank (Wells, Chase, etc.)
8.5%–9.75%
6.50%–7.0%
12 months
20–25% of total project value
Regional CA lender (Pacific Premier, Banner, etc.)
8.25%–9.5%
6.25%–6.75%
12–18 months
20%
Credit union (Logix, Penfed, San Diego CCU, Patelco)
7.0%–9.0%
6.125%–6.50%
12 months
15–20%
Specialty ADU lender (RenoFi, others)
9.0%–11.0%
6.50%–7.0%
12–18 months
10–15% (some lenders)
The "down payment" or equity requirement on construction loans is typically calculated against after-construction value (ACV) — the appraised value of your property after the ADU is built. This is a key distinction from cash-out refi, where equity is calculated against current value.
Worked example
ComponentValue
Current home value$1.0M
ADU project cost$300K
Projected after-construction value (ACV)$1.4M (home + ADU rental income capitalization)
Loan amount$300K (project cost)
Equity required at 20% of ACV$280K — almost your full project cost
Actual cash needed at closeTypically $40K–$80K
ACV-based underwriting is what makes construction loans viable for lower-equity homeowners.
Section 06
When Construction Loan Beats HELOC
The five cases:
Case 01
You don't have $200K+ home equity
HELOCs require existing equity to draw against. If you bought your home in the last 3–5 years and your equity is below $200K, HELOC won't fund the project. Construction loans use after-construction value, so they unlock financing capacity that doesn't exist today.
Case 02
New detached construction over $300K
Larger detached ADUs ($300K+) tax HELOC's draw period. Construction loans are structurally built for this size of project.
Case 03
You want fixed-rate certainty after construction
HELOCs are variable. Construction-to-perm loans lock the perm rate at closing (subject to rate-lock terms). For homeowners who want fixed-rate predictability post-construction, this matters.
Case 04
Your lender requires staged disbursement
Some California construction lenders won't let you draw on a HELOC for new construction over $200K; they require a structured construction loan. This has become more common after the 2024–2025 contractor failure events (Anchored Tiny Homes in Roseville and Multitaskr Construction in Chula Vista, with 550+ projects abandoned combined).
Case 05
You're combining ADU + main-house renovation
Renovation loans (FHA 203(k), Fannie Mae HomeStyle Renovation) bundle the ADU into a single financing structure with main-house work. Cleaner than HELOC + separate construction loan + main-house refi.
Section 07
When Construction Loan Is the Wrong Answer
$200K+ equity AND existing rate below 5%
HELOC is structurally cheaper. Don't trade away your low rate.
Project under $200K
Construction loan overhead doesn't justify the closing costs.
Garage conversion
HELOC's flexibility usually beats construction loan structure for this type.
You want to keep your existing rate
Be careful with construction-to-perm; the perm conversion can reset your existing rate if structured as a refi.
Section 08
Do You Need a Construction Loan, or Does HELOC Pencil?
The case for a construction loan rests on a specific equity position and project structure. For California homeowners with $200K+ existing equity AND a sub-5% existing mortgage, HELOC is structurally cheaper. Run the Lock-In Calculator with your specific numbers.
If construction loan is the right path, the next step is the $199 Feasibility & Risk Assessment, which pressure-tests the project against ACV-appraisal feasibility, the lender's contractor approval requirements, and the inspection cadence for your specific jurisdiction. About 1 in 7 reports recommend not to build. ADUscale is not a lender or financial advisor; we help you find the right financing and connect you with a lender.
A construction loan is just the construction phase: 12 months of staged disbursement, after which you have to refinance into a permanent mortgage (separate closing, separate fees). A construction-to-perm (CTP) loan combines both into one closing: construction phase, then automatic conversion to perm. Most California ADU borrowers should use CTP because it eliminates the second closing's fees and rate-uncertainty risk.
The lender orders a "subject-to-completion" appraisal. The appraiser values the property as if the ADU were already built, based on your construction plans, comparable ADU rental income in your area, and projected resale impact. The valuation is conservative and lender-driven, but typically reflects 75–90% of the actual added value.
Most California construction lenders require the contractor to be CSLB-licensed, insured, and approved by the lender. Some lenders maintain "approved contractor lists." Others are flexible. Construction loans pair well with ADUscale's verified contractor pool, which runs every name through six independent data sources (CSLB license, CSLB disciplinary history, California Superior Court filings, building-department inspections, InspectPilot, and independent insurance/bond verification) and applies eight disqualifying screens.
Most California construction loans allow 1–2 extensions of 3–6 months each, usually for a fee (0.25%–0.5% of loan balance). If construction takes longer than 18–24 months total, you may have to refinance into a different product. Talk to your lender early if you anticipate delays.
Slightly. Typically 700+ for the best rates, vs. 680+ for HELOC. Some California lenders go to 660 with a higher rate. Credit unions are sometimes more flexible.
Yes, but the structure differs. Prefab projects often have a single large delivery + installation milestone rather than the typical 5–7 small draws. Some lenders have specialized "manufactured home" or "modular construction" products with lower rates than traditional construction loans.
Depends on the structure. Stand-alone construction loan: leaves your existing mortgage intact (you have two loans during construction). Construction-to-perm with cash-out: replaces your existing mortgage at perm conversion (this is the lock-in trap to watch for if your existing rate is sub-5%). The "stand-alone" path is what we typically recommend for California homeowners with sub-5% mortgages.
30–60 days typical. Application + docs (1 week), appraisal incl. subject-to-completion valuation (2–4 weeks), underwriting (1–2 weeks), closing (1 week with rescission). Slower than HELOC, faster than purchase mortgages.
The portion used for substantial home improvement (which an ADU typically qualifies for) preserves the mortgage-interest deduction. Talk to your tax professional. We don't give tax advice.
We can share which California construction lenders are most active in the ADU pipeline — we see them in real homeowner files. The best-fit lender depends on your equity position, project type, contractor selection, and credit profile. The Feasibility & Risk Assessment includes a financing-path recommendation calibrated to your specific situation. ADUscale is not a lender, mortgage broker, or financial advisor; we help you find the right financing and connect you with a lender. We do not originate loans or provide investment advice.
About the author · Yaro Korets, Founder of ADUscale
ADUscale is a California build-side ADU partner: we help homeowners secure one of the state's top contractors, expand that contractor's capacity to take the project, and protect the budget with inspection-gated milestone payments — at the same price as going direct. Construction loan analysis is calibrated against current 2026 California lender rate sheets (Federal Reserve H.15), after-construction-value appraisal benchmarks, HUD FHA 203(k) and Fannie Mae HomeStyle Renovation product guidelines, LADBS and San Diego DSD inspection cadence, California HCD ADU policy guidance, and the InspectPilot project finance dataset (11M construction inspection records since 2013).
ADUscale is not a lender, mortgage broker, or financial advisor; we do not originate loans or provide investment advice. This page is informational. Your specific lender will issue a binding quote.
Last updated: May 2026.
Sequence guidance — start with the math
Construction loans are the right answer for new detached ADU projects when HELOC can't fund the full build.
The sequence we recommend: free Reality Check (lot eligibility), free Lock-In Calculator (financing math against your equity position), $199 Feasibility & Risk Assessment (full plan, including ACV-appraisal pressure-testing), then talk to us about a managed build — at the same price as going direct — if the project pencils, or no commitment and a $0 answer if it doesn't. Sometimes the right answer is not to build at all in this rate environment.
