Top HELOC Providers to Build a Granny Flat or ADU

The Quick Read: No single provider tops the list for every owner, because the lenders that write an ADU line depend on occupancy, equity, credit, and whether construction draws are allowed. A mortgage broker that shops several wholesale lenders can match the file to the program that fits.

• Investment-property lines through Lendmire’s network cap at 70% CLTV, with a $500,000 maximum line and a 700 minimum score.
• Primary-residence lines reach 90% CLTV only at a 720 or better score, up to $500,000. Lines up to $750,000 are also possible on primary residences, but they cap at 75% CLTV.
• The line stays variable and is interest-only during the draw period.
• LLCs cannot hold title, so a rental deeded to an entity needs a different route.
• Ask any provider whether draws can fund ground-up construction, not just renovation.

Most roundups hand you a list of company names. A list like that ages badly and ignores your file. This explainer covers what decides whether a HELOC can fund a granny flat, how underwriting treats it, and where the plan breaks.

What Is a HELOC, and Why Do ADU Builders Use One?

A HELOC is a revolving credit line secured by your home. The CFPB describes it as an open-end line you can borrow against repeatedly, with a draw period followed by a repayment period.

ADU builds suit that shape. Costs arrive in stages: design, permits, foundation, framing, finishes. Interest builds on what you have drawn, and the line sits behind your existing first mortgage as a second lien. A cash-out refinance replaces the first mortgage. A HELOC leaves it alone.

An ADU is an accessory dwelling unit: a detached cottage, a garage conversion, or an attached suite. A granny flat is the same idea, usually built for family. The financing mechanics are identical either way.

How Does Underwriting Treat an ADU HELOC, Step by Step?

Underwriting runs in a set order. Each step can stop the file, so it helps to know them before you apply.

1. Occupancy and collateral. The line attaches to the house, not the ADU. Primary residence, second home, and investment property each have different ceilings.

2. Combined loan-to-value. The lender sets a maximum CLTV, subtracts your first mortgage, and the remainder is the possible line.

3. Credit and debt ratio. Primary residences have a 600 program floor, but that score only reaches the lowest CLTV tiers, and the 90% ceiling requires 720 or better. Second homes floor at 640 and investment properties at 700. Debt-to-income tops out at 50%, and the limit falls to 45% for scores from 600 to 679. Qualifying runs on the interest-only payment calculated on the maximum draw.

4. Valuation. Lines at or below $500,000 ordinarily run an automated valuation. Anything above $500,000 requires a full appraisal, and you can request one at any size. The value reflects the house as it stands today, before the ADU exists.

5. Funding. At least 75% of the line is drawn at closing. Later draws carry a $1,000 minimum, except Texas at $4,000.

6. Repayment. When the draw period ends, you can no longer borrow. The CFPB notes that payments are often significantly higher once repayment starts.

That fifth step surprises people. Because so much of the balance arrives up front, the line behaves more like a loan than a flexible build account. Owners who planned to pay contractors strictly in stages should ask each lender how draws work.

What Do the Network’s Programs Allow by Occupancy?

The ceilings are tiered by occupancy, and they differ a great deal.

Each figure is subject to lender guidelines and full file review. Texas primary residences are homesteads and cap at 80% combined loan-to-value, so the higher tiers never apply there.

A line above $500,000 is primary-residence only. It requires a 700 credit profile or better (720 on the longer-runway structure described below), caps at 75% CLTV, and needs a full appraisal.

Which Draw Structures Exist?

Two wholesale structures are common across the programs Lendmire places files with. One runs a 3-year interest-only draw followed by a 17-year amortizing repayment. The other, which this article calls the longer-runway structure, runs a 5-year draw followed by a 25-year repayment. Tennessee shortens both.

Investment lines use the 5-year draw and 25-year repayment structure only, and they carry a 700 minimum score. A line above $500,000 on the longer-runway structure needs a 720 credit profile instead. Both structures float and never convert to fixed, so read the agreement closely. Some owners assume the rate locks during the draw. It does not on these lines.

Experian describes draw periods of five to 10 years, followed by a 20-year repayment period, and notes that some HELOCs carry a balloon payment. That is a market description. The network structures above are the ones that apply to files Lendmire arranges.

Where Does the Plan Break?

Several edge cases can derail an ADU build funded by a line of credit.

Appraisal gap. The finished ADU may appraise below what it cost to build. If you plan to refinance and retire the line, run the numbers on the as-completed value, not the build cost. An improvement may support a higher appraised value, depending on comps and underwriter review. A shortfall means you cover the difference.

Title. The line must be held by an individual borrower or a revocable living trust. LLCs, corporations, partnerships, and irrevocable or land trusts cannot hold title. A rental already deeded to an entity needs a vesting change or a DSCR cash-out refinance instead. That is the sharpest structural difference from a DSCR loan, which can be held in an LLC, subject to lender program eligibility.

Property type. Single-family, 2-4 units, PUD, townhome, and condominium properties are eligible, including non-warrantable condos. Manufactured homes, co-ops, condotels, log homes, commercial, mixed-use, and agricultural zoning are not eligible on either program. Modular factory-built homes work only on the longer-runway structure.

Thin equity. If the line cannot cover the whole project, you may need a second source of funds, such as a construction loan or a renovation-based product. A low CLTV ceiling on an investment property makes this common.

Scarcity. NerdWallet reports that investment-property HELOCs are not offered by all lenders and carry strict requirements. That scarcity is why shopping through a broker matters more here than on a primary-residence line.

Exposure limits. A borrower is limited to three lines, and an owner with more than 15 financed properties is not eligible.

Listing status. A property listed for sale, or listed within the past 60 days, is ineligible in Indiana, North Carolina, Pennsylvania, Tennessee, Texas, and Washington.

Availability. These lines are written in Lendmire’s 16 full-service states: AL, CA, CO, FL, GA, IN, MI, MT, NM, NC, OH, PA, TN, TX, VA, and WA. That is narrower than its 41-market DSCR footprint.

How Does a DSCR Refinance Fit After the Build?

The common pattern is to build with the line, lease up, then refinance. A DSCR cash-out or rate-and-term refinance can pay off the line once the unit is finished. It qualifies primarily on property-level rental income covering the payment, subject to lender guidelines.

The unit must be legal and permitted for its rent to count. A DSCR ratio divides monthly rent by the full monthly obligation (principal, interest, taxes, insurance, and any HOA dues). Clearing the minimum is not the same as positive cash flow, since repairs, vacancy, and management sit outside the calculation.

Cash-out refinances on standard rentals generally top out around 75% LTV, with about 6 months of seasoning expected. Short-term rental collateral is lower, at 70% on a cash-out. DSCR is not offered on manufactured homes, log homes, or barndominiums. Lendmire’s complete DSCR loans guide covers the full parameter set, and its piece Best Investment Property HELOC Program to Build a Granny Flat or ADU goes deeper on the rental side of the line itself.

Key Terms Defined

CLTV: Combined loan-to-value, meaning all liens on the property divided by its value.

Draw period: The stretch in which you can borrow against the line, usually interest-only.

Repayment period: The phase after the draw ends, when the balance amortizes and no new draws are allowed.

Second lien: A loan that sits behind your first mortgage in repayment priority.

DSCR: Debt service coverage ratio, meaning monthly rent divided by the full monthly property obligation.

Who Should Skip a HELOC for an ADU?

Skip it if you need a fixed payment, because these lines float throughout. Skip it if your equity is thin, since a 70% investment ceiling leaves little room after a first mortgage. Skip it if the property sits in an LLC. And skip it if a lender will only allow draws for renovation, not ground-up construction.

For the family-use granny flat on a primary residence, the picture improves. Ceilings are higher and the credit floor is lower. For a rental ADU on an investment house, plan on tighter leverage and a bigger gap to fill.

How Do You Find the Right Provider Through a Broker?

Lendmire is a mortgage broker. It works with a nationwide network of wholesale HELOC lenders and does not lend directly. The best program for your situation depends on occupancy, credit profile, leverage need, and how you hold title. A broker can match the scenario to a program rather than sending you to one counter.

Before you apply, gather this list:

• Current first-mortgage balance and a realistic value estimate
• Credit profile and housing history across all financed properties
• Whether the home sits in your name or a revocable trust
• The permit path and a contractor draw schedule
• A plan for any funding gap

If you are considering a home equity line and want to see how the numbers work, Lendmire can help you compare HELOC options based on the property, the equity available, credit profile, combined leverage, and your goals. For a primary-residence version of the same question, see Lendmire’s guide Best HELOC Program to Build a Granny Flat or ADU. Request a quote at 828-256-2183.

About Lendmire

Lendmire (NMLS# 2371349) is a mortgage brokerage serving homeowners and real estate investors in its 16 full-service states. Home equity lines of credit are arranged through wholesale lending channels; Lendmire brokers the line and the lender underwrites each application under its occupancy-based guidelines. Scotsman Guide named Lendmire a Top Mortgage Workplace in both 2025 and 2026.

References

1. CFPB

2. Experian

3. NerdWallet