ADU Construction Loan: Types, Draws and Example

By ADU Scope editorial team | Last verified: October 2026
An ADU construction loan pays for your build in stages and lends against the property’s value once the unit is done. There is no single product with that name. Instead, you choose between three families: a construction-to-permanent loan, a renovation mortgage, or short-term financing followed by a refinance.

Our view: if you are buying a home or refinancing anyway, a single-closing renovation mortgage is usually the simplest route. If you already own with a low-rate mortgage, however, compare a HELOC before you refinance everything. This article is general information, not financial advice, and every number below is either dated and sourced or labelled hypothetical.

How an ADU construction loan works

A regular mortgage lends against a house that already exists. An ADU does not exist yet, so the lender must decide how much to lend against something unbuilt. As a result, any ADU construction loan involves approved plans, an approved contractor and funds released in stages.

First, the lender approves your budget and plans. Then it releases money in draws as work passes inspection. Finally, an appraisal confirms the finished value and the loan moves to its permanent terms.

For an ADU, the key concept is the as-completed appraisal. It estimates the property’s value after the unit is built. You can then borrow against that value, not only today’s equity. That matters most when you have limited equity.

If you are still pricing the project, start with our guide to how much an ADU costs in California. Lenders size the loan to your budget, so a realistic number comes first.

Which ADU construction loan types exist

Three families of ADU construction loan cover almost every case. The table shows how they differ before we go through each one.

Loan family	Closings	How you pay during the build	Best fit
Construction-to-permanent	One	Usually interest on the amount drawn	Building a new home plus an ADU
Renovation mortgage	One	Set by the program, with draws from escrow	Buying or refinancing with an ADU in the plan
Short-term loan, then refinance	Two	Whatever the short-term lender sets	Owners who need speed and accept refinance risk

Construction-to-permanent loans

Fannie Mae says borrowers building a new single-unit property with an ADU can use this loan for both the home and the ADU. It also says any Selling Guide loan product can finance an ADU. In general, you close once and draw funds during construction. The loan then converts to a permanent mortgage when the work ends.

Details vary by lender, so ask for these in writing:

Loan-to-value limits and the down payment.
Whether payments during construction are interest only.
The inspection steps before each draw.
How the final appraisal sets the permanent loan.

Fannie Mae also lists exclusions. Per its ADU page, ADUs are not eligible with a two- to four-unit dwelling or a manufactured home as the primary residence. Properties with multiple ADUs are also ineligible. Confirm your property fits before you apply.

Renovation loans that act as an ADU construction loan

Fannie Mae HomeStyle Renovation lets you purchase or refinance a one-unit property and construct or install a new ADU. Freddie Mac says its CHOICERenovation allows the addition or renovation of ADUs, and HUD allows ADUs under the FHA 203(k). Our guide to ADU renovation loans compares the limits side by side.

Freddie Mac describes CHOICERenovation as always a single closing with no interim construction financing. The loan finances improvements, and you complete them after closing. That differs from a traditional construction loan, where the lender funds the build before the permanent loan starts.

Short-term loan plus a refinance

Some owners borrow short term, build, and then refinance. Freddie Mac says CHOICERenovation can include a no-cash-out refinance to pay off short-term financing used for ADU work. The path works, but it carries timing risk.

If rates rise or your income changes before the refinance, you could face a higher rate or fail to qualify. For that reason, treat this route as the riskiest of the three. Ask each lender what happens if you cannot refinance.

Worked example: ADU construction loan costs (hypothetical)

This example shows how interest builds on an ADU construction loan and what the permanent payment looks like. It is hypothetical and not a quote. The rates in it are illustrative, except where we cite Freddie Mac.

Inputs:

Total loan of $200,000, drawn in four equal steps of $50,000 over 12 months.
Construction-phase rate of 8.5%, interest only, hypothetical.
Permanent loan of $200,000 at 7.28% for 30 years, or 6.60% for 15 years. These match Freddie Mac’s weekly averages for October 1, 2026.

During construction the balance is $50,000 for months 1 to 3, then $100,000, $150,000 and $200,000 for each following quarter. Interest across the year therefore totals about $10,625. That is $1,062.50, $2,125.00, $3,187.50 and $4,250.00 per quarter.

After conversion, the principal and interest payment is about $1,368.42 a month on the 30-year loan. On the 15-year loan it is about $1,753.23. Those figures exclude taxes, insurance and mortgage insurance.

The lesson is simple. Interest during the build is real money, so a faster schedule costs less. Budget for it, and for the surprises covered in our guide to hidden ADU costs and utility hookups.

What an ADU construction loan costs beyond the rate

The interest rate is only one line. Ask each lender for a Loan Estimate that shows every fee, because an ADU construction loan usually adds work that a plain mortgage does not.

Origination or lender fees, which differ by lender.
An as-completed appraisal, and sometimes a second appraisal at the end.
Inspection fees before each draw.
Interest on drawn funds during the build.
Title or draw fees charged at each release, where the lender applies them.

In addition, keep a cash cushion outside the loan. Cost overruns are a classic problem, and lenders rarely fund them. Ask what happens if the budget grows, and whether the lender lets you rebalance the draw schedule.

Which ADU construction loan should you choose?

Start with your situation, because the right loan follows from it.

Buying a home and planning an ADU: use a renovation mortgage. One closing and one payment keep things simple.
Building a new home with an ADU: ask about construction-to-permanent financing.
Owning with a low-rate mortgage: compare a HELOC first, since a new first mortgage would replace your current rate.
Needing speed and willing to carry risk: short-term financing can work, but plan a backup if the refinance fails.

Whatever ADU construction loan you choose, get three written quotes. Compare them on total cost, not only the headline rate.

Can ADU rent help you qualify?

Rules differ by program, and a lender decides case by case. According to the sources we checked:

FHA: ADU income may count as effective income, up to 30% of total monthly effective income used to qualify. Borrowers without rental history can use an appraiser’s rent schedule.
Freddie Mac: lease-documented ADU income counts at up to 75% of the lease. It can make up no more than 30% of qualifying income, and it applies to purchases and no-cash-out refinances. We did not confirm that projected rent for an unbuilt ADU counts.
Fannie Mae: its rules on ADU rental income differ by loan type. Ask the lender and check Selling Guide B3-3.1-08 and B3-3.8-01.

Our article on ADU rental income and loan qualification goes deeper.

Questions to ask before you pick a lender

Use the same list with every lender, then compare the written Loan Estimates. Our scorecard in how to choose an ADU lender turns these into a grid.

Do you finance ADU construction, and which program do you use?
How do you determine the as-completed value, and does it include the ADU?
What are the maximum loan-to-value and the down payment?
Who approves the plans and contractor?
How are funds released, and what inspections apply?
What rate and fees apply during construction and afterward?
What happens if costs exceed the budget?
What if I cannot refinance or convert the loan?

Frequently asked questions

Is an ADU construction loan different from a HELOC?

Yes. A HELOC borrows against equity you already have. An ADU construction loan or renovation mortgage lends against the as-completed value. It also controls how funds are released.

Can I get a loan to build an ADU on a home I do not own yet?

Possibly. Fannie Mae HomeStyle and Freddie Mac CHOICERenovation both apply to purchases as well as refinances. Each lender sets its own conditions.

Which loan costs the least?

We cannot say without quotes. Compare total interest and fees from at least three lenders, using the same loan amount and term.

Sources

General information, not financial advice. Loan terms change, so confirm every figure with a lender.

ADU Construction Loans: How They Work and Which Loan Types Exist