Thinking about building or financing an ADU in Sammamish but not sure how lenders and appraisers will treat it? You are not alone. Many owners want the rental income to help qualify or expect a premium in value, yet the process can feel opaque. In this guide, you will learn how ADUs are evaluated, what rent rolls need to show, and how to assemble rent comps that underwriters will accept. Let’s dive in.
What lenders look for in Sammamish ADUs
Start with permits and legal status
Lenders and appraisers want clear proof that the ADU is legally permitted by the City of Sammamish. Expect to provide the final building permit, final inspection or certificate of occupancy, and any zoning compliance evidence. If the ADU is not permitted, many lenders will not give it value and may exclude the rental income.
Function and utility features
Appraisers document how the ADU functions. Separate entrance, kitchen, bathroom, heat, and safe egress matter. Utilities and metering also matter. Shared or separate meters and proper sewer or septic connections affect both marketability and underwriting confidence.
Market acceptance on the Eastside
Sammamish sits in a high-demand Eastside market with strong renter interest tied to regional employment. Even so, value premiums must be proven with comparable sales that include ADUs. If local comps are limited, expect conservative treatment of both value and income.
How appraisers value homes with ADUs
Sales comparison first
For most single-family homes, the sales comparison approach drives value. The appraiser looks for nearby sales of homes with ADUs and adjusts for differences. If the market consistently pays a premium for ADUs, that premium will appear in the adjusted comparable sales.
Income approach when rents are reliable
If ADUs are commonly rented and rent data is available, an appraiser may use an income approach. This can include a gross rent multiplier or income capitalization when there are enough credible rent comparables. The appraiser often supports market rent using a comparable rent schedule such as Form 1007.
Cost approach for new builds
For new or custom ADUs where comps are scarce, the appraiser may reference the cost to build. Remember, cost does not always equal market value. Market acceptance still drives the final opinion of value.
Documentation appraisers include
Expect a full URAR report with addenda that describe the ADU, photos, floor plans, and permits. For rent support, the appraiser may include a comparable rent schedule with nearby rental comps. Clear, organized documents help the appraiser and reduce underwriting questions.
How lenders treat ADU rental income
Existing leases and tax history
If the ADU is already rented, lenders lean on the actual lease and tax returns to determine income. A 12-month lease and Schedule E from your tax return are common proofs. Many programs count a portion of net rental income after expenses according to their guidelines.
Projected rent for a new ADU
If there is no lease history, lenders may accept projected rent supported by market comparables and an appraiser’s rent conclusion. Underwriters often reduce projected gross rent for vacancy and expenses before adding it to qualifying income. The reduction varies by program and lender, and many use a conservative allowance.
Short-term rentals versus long-term
Most conventional lenders and many government programs do not accept short-term rental income for qualifying unless there is a stable long-term history. Appraisers also tend to view short-term income as less predictable. Long-term leases are the stronger path for underwriting.
Program and lender differences
Conventional, FHA, VA, and portfolio lenders can have different rules and overlays. Some local banks and portfolio lenders are more flexible on rent treatment. Confirm policies up front so you know how much income will count and what documents are required.
Build realistic rent comps in Sammamish
Match unit type and location
Compare detached ADUs to other detached ADUs and attached units to similar attached units. Keep comps in Sammamish or immediately adjacent neighborhoods with similar lot size, privacy, and parking. Eastside submarkets differ, so avoid stretching to dissimilar areas when better local data is available.
Use multiple sources
Underwriters prefer verifiable rental data from multiple sources. Combine appraiser-supported rent schedules with MLS rental history or local property management surveys. Aggregators can supplement, but stronger sources carry more weight in underwriting.
What a strong rent roll includes
A clear rent roll helps the underwriter trust the income. Include:
- Property address and unit label
- Tenant name, lease start date, and term
- Monthly rent and security deposit
- Who pays which utilities
- Proof of payments when available, such as canceled checks or deposit records
Step-by-step path to financing
- Confirm zoning and permits. Speak with the City of Sammamish planning and building teams early. Get clarity on size limits, parking, utility connections, and any owner-occupancy rules.
- Complete legal permitting. Lenders almost always require final permits and inspections. Unpermitted work risks exclusion from value and income.
- Choose an ADU-competent appraiser. Share permits, plans, photos, and any rent history or rent research before the visit.
- Assemble rent documentation. If rented, provide the lease, rent roll, payment history, and Schedule E. If not yet rented, provide an appraiser-supported rent schedule, local rent comps, and a simple marketing plan.
- Select the right loan type. Consider construction-to-perm for a new build or refinance after completion if you want the new value included. If income is critical for qualifying, discuss portfolio options.
- Expect conservative underwriting. Plan for vacancy and expense deductions from gross rent and be ready to supply extra comps if rent drives your qualification.
Lender-ready checklist
- Final building permit and final inspection or certificate of occupancy for the ADU
- Floor plans and a site plan showing the ADU layout and access
- Clear photos of interiors, exteriors, and any separate utilities or parking
- Executed lease and rent roll with payment evidence, if applicable
- Appraiser-supported market rent schedule and local rent comparables
- Appraisal report stating the ADU’s legal status and rent conclusion
- Schedule E tax pages if the ADU has prior rental history
- Construction contract, draw schedule, and lien releases for new builds
- Insurance confirmation that the ADU use is covered
Set the right expectations
- Permits drive value and income treatment. A finaled, code-compliant ADU is far easier to finance.
- Pro forma rent is scrutinized. Strong comps and appraiser support help, but expect deductions for vacancy and expenses.
- Short-term rents rarely count. Long-term leases are more credible to underwriters.
- Lender overlays vary. Get a written pre-approval that addresses how ADU rent and value will be treated.
If you want a calm, organized path from planning to appraisal to closing, we can help you prepare the right documents, coordinate with your appraiser, and align your strategy with realistic lender expectations. Reach out to the Six Degrees Team to talk through your goals and next steps.
FAQs
How do appraisers value a Sammamish home with an ADU?
- Appraisers prioritize comparable sales with ADUs, then may use an income approach if rents are reliable, and a cost reference for new builds. Legal permits and market acceptance are central.
What permits do lenders want for an ADU in Sammamish?
- Lenders usually require a final building permit and final inspection or certificate of occupancy, plus evidence of zoning compliance and proper utility connections.
Can I use projected rent from a new ADU to qualify?
- Many lenders allow projected rent supported by an appraiser’s rent schedule and strong comps, but they often deduct for vacancy and expenses before counting it toward your income.
Will short-term rental income help me qualify for a mortgage?
- Most conventional and many government programs do not accept short-term rental income unless there is a stable long-term history. Long-term leases are stronger for underwriting.
What should a lender-ready rent roll include for an ADU?
- Include the unit label, tenant name, lease dates, monthly rent, deposit, utility responsibility, and proof of payments. Clarity and consistency reduce underwriter conditions.
How do I choose the right comps for an ADU in Sammamish?
- Match the ADU type and privacy level, stay in Sammamish or adjacent areas, and use multiple credible sources. Detached compares to detached, and attached to attached.
