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An ADU construction loan pays for a backyard unit in stages. The lender approves your plans, contract and budget, then releases money in draws as work reaches agreed milestones and its inspector confirms progress. You pay interest only on what has been released, and at completion the loan converts to permanent financing or is paid off.
We already have a general article on how a construction loan works for any type of building project. This is the ADU-specific version: what changes when the project is a second dwelling on a lot you already own, how the draw schedule lines up with a cottage build, and how United Signature coordinates with the lender so the site never waits for money.
What Makes a Backyard Unit an Unusual File for a Lender
Most construction lending is designed either for a new house on vacant land or for a renovation of an existing house. An ADU sits between the two. It is a new, separate dwelling, but it shares a parcel, a title and often utility connections with a home that is already standing and usually already mortgaged.
That raises practical questions a lender has to answer. Will the loan replace the existing mortgage or sit behind it in second position? Will the appraiser value the property with the finished ADU, and are there nearby sales of homes with ADUs to support that value? Is the builder experienced with detached units? Lenders that answer these questions routinely make the process much smoother, which is one reason to ask early whether a lender has closed ADU construction loans before.
The Package a Lender Wants to See
Plans, Specifications and Permit Status
The lender needs construction drawings and a description of materials and finishes, so its appraiser can value the completed property and its inspector can measure progress against something concrete. Many lenders will not release the first construction draw until the building permit is issued.
A Signed Contract and a Line-Item Budget
A fixed contract price, broken down by category or trade, lets the lender compare each draw request with the budget line it belongs to. A budget that lumps everything into a few large numbers makes draw approvals slower and invites questions.
A Schedule That Matches the Budget
A schedule showing when each stage should start and finish allows the lender to plan inspections and lets everyone see early when a stage is running long. For the full phase-by-phase picture of an ADU project, see our guide to a realistic ADU timeline.
How the Draw Schedule Is Built Around Milestones
The draw schedule divides the loan into payouts tied to visible progress. For a detached ADU, milestones usually follow the natural order of the build: site work and foundation, framing with roof and windows, rough-in of plumbing, electrical and mechanical systems, insulation and drywall, then finishes, fixtures and final completion.
United Signature bills after each trade is completed and verified, which fits a milestone-based draw schedule well. The key is to agree on the schedule before work starts, so that each invoice from the builder corresponds to a draw the lender has already planned for. Some lenders hold back a portion of each draw until the project is finished, which protects the lender but needs to be reflected in the payment plan agreed with the builder.
Lender Inspections Are Not City Inspections
Two separate sets of inspectors will visit the site, and they look for different things.
City inspectors check code compliance: foundation and reinforcement, framing, plumbing, electrical and mechanical rough-ins, insulation and the final inspection before occupancy. Passing them is required to continue and, at the end, to occupy the unit.
The lender’s inspector checks progress and value: whether the work claimed in a draw request is actually in place and whether the remaining loan balance is enough to finish. The lender’s inspector does not approve code compliance, and a passed city inspection does not automatically release a draw. On many projects, the draw request is timed shortly after the related city inspection so that both confirm the same milestone. The lender may also order a title update before each draw and ask for lien waivers showing that subcontractors and suppliers were paid from the previous one.
What You Pay Each Month While the Unit Is Built
During construction, most loans require interest-only payments calculated on the amount disbursed so far. Early in the project, when only the first draws have been released, the payment is modest; by the final stages, it reflects nearly the full loan. Many homeowners pay these from income, and some loans allow the interest to be funded from a reserve set aside within the loan.
Budget for the full sequence, not just the first month. If the build runs longer than scheduled, interest-only payments continue for the extra months, and some loans charge a fee to extend the construction period. Ask the lender how extensions work before closing.
Contingency Inside the Loan
Lenders want to see that the project can be finished even if something costs more than planned. Many require a contingency line within the loan budget or proof of cash reserves outside it. For an ADU, the usual sources of surprises are utility connections, soil and foundation conditions, and work required by the city during review.
Money in a contingency line is typically released only for documented changes, often with the lender’s approval of a change order. Our article on setting a remodel contingency explains how to decide how large that cushion should be.
When the Build Ends: Conversion or Payoff
A construction-to-permanent loan, sometimes called a single-close loan, converts into a regular mortgage after completion, with one set of closing documents at the start. A standalone construction loan has to be paid off at completion, usually with a new mortgage, a refinance or a home-equity product, which means a second approval and a second closing.
The conversion or payoff typically requires proof that the city’s final inspection has passed and the lender’s own final inspection is complete. Single-close loans reduce paperwork and the risk of not qualifying at the end; two-step financing can leave room to shop for a better permanent loan later. Homeowners who prefer a revolving credit line for the build instead of a draw-based loan can compare that route in our guide to using a HELOC for an ADU, and our ADU financing overview places both alongside the other options.
How the Builder and Lender Keep Money Moving
Smooth draws come from preparation. Before construction, the builder, lender and homeowner should agree on the draw schedule, the documents required with each request, how the inspector will be scheduled and who receives the funds. During construction, the builder submits invoices with photos and any lien waivers, the homeowner approves the request, and the lender inspects and releases funds.
Delays usually come from missing paperwork or a draw requested before the milestone is fully complete. A builder used to lender-funded projects plans for these steps and keeps the site moving. To see how United Signature runs an ADU project from permit to move-in, visit the ADU construction page, and review current financing options if a partner product could cover finishes outside the loan.
FAQ
Can I act as my own general contractor on an ADU construction loan?
Most lenders will not allow it. They typically require a licensed, insured contractor with a signed fixed-price contract, because an experienced builder lowers the risk that the project stalls halfway.
Who pays for the lender’s draw inspections?
The borrower usually does, either per inspection or through a fee built into the loan. Ask for the inspection cost and the expected number of draws before closing so the total is part of your budget.
What happens if the lender’s inspector finds a stage unfinished?
The draw is typically reduced to match the completed work or delayed until the stage is done. The builder then resubmits, which is why requests should be timed to finished milestones rather than nearly finished ones.
Can I change finishes after the construction loan closes?
Yes, but most lenders require a written change order and may need to approve it, particularly if it changes the budget. Upgrades that raise the cost usually have to be paid from your own funds or from contingency.
Does the lender pay the builder directly or pay me?
It depends on the lender. Some release draws to the builder or into an escrow or title account, while others pay the borrower, who then pays the builder; agree on the method before the first draw.