1500 Sq Ft ADU Cost in Portland, OR
A 1500 sq ft ADU in Portland, OR costs roughly $574,000–$980,000 all-in for 2026, including permits, utilities, and soft costs. Adjust the slider to see other sizes.
Cost Breakdown (Mid-Range)
| Category | Amount | Share of Mid Total |
|---|---|---|
| Hard construction (labor + materials) | $637,500 | 86% |
| Soft costs (design, engineering, PM) | $76,500 | 10% |
| Permit and impact fees | $16,500 | 2% |
| Utility hookups | $9,000 | 1% |
| Mid-range total | $739,500 | 100% |
Last updated April 2026.
Building a 1500 Sq Ft ADU in Portland: What's Specific Here
Portland's Residential Infill Project (RIP) opened nearly every R-zoned lot to ADUs and triplex conversions, and the city waives System Development Charges (SDCs) for ADUs entirely — that alone saves $8,000-$18,000 versus pre-2018 builds. The catch is Portland's wet climate: foundation drainage, deck flashing, and rain-screen wall assemblies are not optional, and a builder who's only worked in dry climates will under-bid the moisture detailing. For a 1500 sq ft build specifically, expect 12-20-week plan review through Portland Permitting & Development (PP&D) and a build sequence shaped by the city's wet temperate climate and Oregon Residential Specialty Code, Portland Zoning Code 33.205, RIP rules requirements.
What a 1500 Sq Ft ADU Actually Gets You
A 1500 sq ft ADU in Portland, OR is a spacious 3-bedroom. At this size you'll deal with the standard Portland, OR permit path and city-specific code requirements (Oregon Residential Specialty Code, Portland Zoning Code 33.205, RIP rules).
Cost by Build Method
| Build method | Low | Mid | High | Notes |
|---|---|---|---|---|
| Stick-built (custom) | $574,200 | $739,500 | $979,800 | Most common path; highest cost, most layout flexibility |
Realistic Build Timeline for 1500 Sq Ft in Portland
| Milestone | Typical duration |
|---|---|
| Design + construction documents | 4-8 weeks |
| Portland, OR permit submission + review | 12-20 weeks |
| Site prep + foundation | 4-6 weeks |
| Framing + rough-ins (MEP) | 9-13 weeks |
| Finishes + final inspection | 11-15 weeks |
| TOTAL (design → certificate of occupancy) | 40-62 weeks |
Financing a $740,000 1500 sq ft ADU in Portland, OR
Most Portland, OR homeowners stack a cash or HELOC down payment with a construction-to-perm loan. Sample scenario for a mid-range 1500 sq ft build:
| Total project cost (mid) | $739,500 |
| 20% down payment (cash or HELOC) | $147,900 |
| Loan principal (80%) | $591,600 |
| Estimated rate (May 2026) | 7.5% (30-year) |
| Estimated monthly payment | $5,171 |
| Estimated rent (1500 sq ft in Portland, OR) | $1,760–$2,990/mo |
| Break-even rent target | $5,171/mo |
Sample scenario only — your actual rate, term, and rent will vary. Use the loan calculator to plug in your numbers.
Portland Permit Fee Detail
| Plan check | $800–$2,000 |
| Building permit | $1,500–$3,500 |
| Impact fees | SDC waived for ADUs |
| School fees | N/A |
| Utility hookups | $2,000–$6,000 |
Questions to Ask Portland ADU Contractors
Before signing with a contractor for your 1500 sq ft ADU in Portland, OR, ask:
- How many full 1- and 2-bedroom ADUs have you completed in Portland in the last 24 months?
- What's your average permit timeline with Portland Permitting & Development, and how do you handle plan-check correction cycles?
- Do you handle Pacific Northwest moisture detailing (rain screens, deck flashing, foundation drainage) in-house or sub it out?
- What's specifically included vs. excluded in your turnkey quote — soft costs, utility tap fees, landscaping, driveway repair?
- What's your payment schedule, and what triggers a change order vs. an allowance overrun?
- Can you provide addresses for 2-3 completed Portland ADU projects I can drive by?
How We Calculate This
These are 2026 all-in market estimates. Hard costs scale linearly with square footage using a low/mid/high per-sq-ft band calibrated to recent build data in each metro. Soft costs (design, engineering, project management) are applied at ~12% of hard costs. Permit and utility hookup fees are set to local base amounts and lightly adjusted for size. For an itemized estimate tied to your lot, finish level, and specific city jurisdiction, use our Cost Estimator.
Get 3 Contractor Quotes
We match you with licensed ADU contractors in Portland, OR. Free, no obligation.
Frequently Asked Questions
How much does a 1500 sq ft ADU cost in Portland, OR?
A 1500 sq ft ADU in Portland, OR typically costs $574,000–$980,000 all-in for 2026. The mid-range estimate is $740,000, which includes hard construction ($637,500), soft costs ($76,500), permit fees ($16,500), and utility hookups ($9,000).
What is the price per square foot for ADUs in Portland, OR?
For a 1500 sq ft build in Portland, OR, expect $383–$653/sq ft all-in. The mid-range is roughly $493/sq ft. Per-sq-ft cost falls slightly at larger sizes because permit and utility fees amortize over more square footage.
How long does a 1500 sq ft ADU take to build in Portland, OR?
Total timeline runs 40-62 weeks from design start to certificate of occupancy in Portland, OR. Permits alone take 12-20 weeks through Portland Permitting & Development (PP&D), followed by 24+ weeks of construction. Pre-approved plans and prefab paths can shorten the permit phase.
Can I finance a $740,000 ADU in Portland, OR?
Yes. For a $740,000 mid-range build, common options are construction-to-permanent loans, HELOC, cash-out refinance, or RenoFi. At current ~7.5% rates, a fully-financed build is roughly $5,171/month on a 30-year term. Use the ADU loan calculator to compare products side by side.
What size of ADU is allowed in Portland, OR?
Portland, OR permits detached ADUs up to 800 sq ft on most lots. A 1500 sq ft unit is above the typical limit, so it generally requires an attached/duplex configuration or a variance.
What rent can I expect from a 1500 sq ft ADU in Portland, OR?
In Portland, OR, 1500 sq ft ADUs rent for approximately $1,760–$2,990/month based on 2026 market rents for comparable units. Newer construction with separate parking and a private entrance lands at the high end of that range.
What's the difference between a 1500 sq ft and a 2000 sq ft ADU in Portland, OR?
A 1500 sq ft Portland, OR ADU comes in around $740,000 mid-range, while the next bucket up at 2000 sq ft runs about $980,000 — roughly $241,000 more. The bigger size adds a bedroom or larger living area but still falls within the city ADU size cap.
What's the most common mistake when building a 1500 sq ft ADU in Portland, OR?
Underestimating the pacific northwest moisture detailing (rain screens, deck flashing, foundation drainage) requirement — many homeowners get bids from contractors who don't price these into the quote, then face change orders mid-build. Always confirm in writing how pacific northwest moisture detailing (rain screens, deck flashing, foundation drainage) is handled before signing.
Keep Planning Your Portland, OR Build
See Other Sizes in Portland
Done Estimating? Track Your Real Costs.
TerraLine picks up where the estimator leaves off — track actual spend vs budget, manage draw schedules, and know exactly where every dollar goes during construction.