Housing model profileADUAddress checking pending
Attached / basement ADU
1 new home inside the existing house, main home kept
Turn part of your existing house into a complete home for family or a renter, with its own kitchen, bathroom, and entrance. This model covers interior conversion; an addition needs a separate design and budget.
Model published; address matching is pending
Published concept; address matching and cost calibration are pending. A measured interior assessment is required.
Urban Acupuncture housing model
Published housing concept and illustrative schematic. Address checking is pending; these are not City-pre-approved construction drawings.
- Homes
- 2
- Building type
- Main home plus one interior accessory dwelling unit
- Existing house
- Keep + convert
- You end up with
- 1 new home inside the existing house, main home kept. Keep the main home; convert a basement or other interior space into one additional home.
- You put in
- Renovation or construction funds, cash or borrowed; ongoing operating costs. Get a site-specific budget before committing.
- Your role
- Owner commissioning the work; landlord if rented, or host for family housing.
- Timeline
- Interior/site assessment → design and permits → construction → occupancy. Ask the designer and contractor for durations; no project schedule is established here.
- It works when
- The current rules allow an attached accessory dwelling unit in this house; The measured interior can accommodate a complete home and safe independent access; Ceiling height, emergency escape, fire separation, moisture control, and utilities can be resolved.
- Main uncertainty
- Renovation/site costs and rent may leave a monthly loan shortfall. Family use does not produce rental income.
- Next step
- Bring measured plans or a survey to a residential designer, then request a contractor budget and financing proposal.
Representative site plan
One accessory home within the existing house; interior layout to be measured. Drawn on a typical lot — every real lot differs, so this is illustrative, not a site-specific layout.
The program
2 homes — main home retained + one interior accessory home.
+1 net new home per lot (market-rate).
Cash-funded vs. financed rental
Enter your contractor's all-in budget, achievable rent, and annual operating costs including added property tax. No renovation-cost or rent estimate has been calibrated for this model. The 100% loan share, 7% rate, 30-year term, and 5% vacancy are editable illustrations, not financing offers or market estimates.
Enter a positive budget and complete valid assumptions to see the comparison.
Include design, permits, utilities, tax, contingency and construction-period financing in the all-in budget. This amortizing-loan comparison excludes loan fees, replacement reserves, owner income taxes and appreciation. Family occupancy produces no rent; enter zero rent to model it.
Where it fits
An existing house with space for a second complete home and a practical separate entrance. A basement needs particular attention to ceiling height, daylight, emergency escape, moisture, and drainage. Lot data alone cannot establish interior fit.
What must be true
- The current rules allow an attached accessory dwelling unit in this house
- The measured interior can accommodate a complete home and safe independent access
- Ceiling height, emergency escape, fire separation, moisture control, and utilities can be resolved
Verify before relying on it
- Measured floor plans, ceiling heights, structure, and a designer's code review
- Basement drainage, moisture, sewer elevation, and any excavation or underpinning
- Contractor renovation budget, achievable rent, and owner financing
Published concept; address matching and cost calibration are pending. A measured interior assessment is required.
Start with Seattle SDCI's accessory dwelling unit guidance, then ask a residential designer to review the measured interior against current requirements.
Funding and programs that may apply
Programs that may pair with this plan
Matched from plan facts only. Parcel geography, income, utility territory, and owner facts can change the final list.
Home Improvement Property Tax Exemption
King County Assessor / RCW 84.36.400
Temporary property-tax exemption on qualifying added improvement value.
Exempts added value up to 30% of original structure value
Washington State HEAR Electrification Rebates
Washington Department of Commerce / local HEAR administrators
Administrator-run rebates for eligible electrification equipment and installation. Measures, amounts, coverage and available funding vary by local administrator.