Build a backyard cottage in Portland: the project workflow

Building a backyard cottage in Portland takes 12 to 22 months and pulls you through four city bureaus (PP&D, BES, PWB, PBOT), one investor-owned electric utility (PGE), and 8 to 14 separate pros. The lever that swings your budget more than anything else is System Development Charges. At full rate they're roughly $18,000 to $25,000 (PP&D's 2023 sample table for a detached ADU lands at about $18,962 across BES, PWB, PBOT, and Parks). The good news: Portland's ADU SDC Waiver is still active. If you own and live on the lot or rent month-to-month, a 10-year no-short-term-rental covenant drops that bill to near zero. A separate citywide exemption also covers housing units permitted between 2025-08-15 and 2028-09-30. This is the order most builders actually run the project. Click any step on the project map to read the detail. Steps stacked side-by-side run in parallel.

1. Phase 0

   Feasibility

   Four free or near-free checks tell you whether a DADU actually fits your lot before you spend a dollar on design: zoning, SDC waiver eligibility, water service, and trees. Run them in parallel and you'll have answers in 2-4 weeks.

   2-4 weeks·Free·4 steps
   1. 4 in parallel
      0.1Confirm a DADU is allowed on your lotPull your parcel up on Portland Maps and check the zone, the base allowances, and any overlay that limits accessory structures. About a minute of work, and it tells you whether to keep going.Homeowner, PP&D1 day · Free0.2Estimate SDCs and check waiver eligibilitySystem Development Charges run roughly $18K-$25K at full rate, but Portland's ADU SDC Waiver and a 2025-2028 citywide exemption let most projects skip them. Figure out which discount applies before you set a budget — it moves the number by an order of magnitude.Homeowner, Bureau of Environmental Services1-2 weeks · Free0.3Confirm water service from PWBPortland Water Bureau decides whether your existing meter can serve a second unit or you need a new tap. A new tap adds $5K-$15K plus the PWB SDC, so the free inquiry is worth doing first.Homeowner, Portland Water Bureau1-3 weeks · Free inquiry0.4Walk the lot for protected treesTitle 11 Chapter 11.50 protects trees ≥12" DBH on your development site, and trees ≥20" DBH have to stay unless an exemption applies. Walk the lot now so your designer draws a footprint that fits the first time.Homeowner, Urban Forestry, Arborist1 day · Free (DIY) or $400-$800 (arborist consult)
2. Phase 1

   Site facts

   Turn your lot into the measured documents your designer and PP&D reviewers will ask for: survey, geotech if needed, and electrical service capacity.

   3-6 weeks·$2,500-$8,000·4 steps
   1. 3 in parallel
      1.1Order a site surveyAn Oregon-licensed surveyor gives you a boundary + topographic survey, which becomes the base layer for every drawing that follows.Homeowner, Surveyor2-4 weeks · $2,000-$4,0001.2Geotech report if landslide / steep slope flaggedIf Portland Maps flags a hazard or your lot slopes ≥25%, you need a geotechnical investigation. This isn't optional on flagged lots.Homeowner, Geotech eng.3-5 weeks · $3,500-$7,5001.3Verify PGE service + main panel capacityPGE (not the city) supplies your power. Most DADUs need a 200A panel upgrade or a separate sub-panel; some need a fresh service line from PGE. File the request now — lead times can run 6-16 weeks.Homeowner, Electrician, Portland General Electric1-2 weeks · $300-$800 (electrician walk-through)
   2. 1.4Measure-up the existing houseIf you're sharing utilities, walls, or a driveway with the primary house, you need accurate as-builts of what's already there. Saves the design from being redrawn at intake.Homeowner, Designer1-2 weeks · $800-$2,000
3. Phase 2

   Design

   Turn the site facts into a permittable design. A pre-approved plan set shortens this a lot; a custom design runs 3-5 months.

   3-5 months (custom) / 4-8 weeks (pre-approved)·$8,000-$28,000·5 steps
   1. 2.1Choose: pre-approved plan vs. custom designerPortland accepts pre-approved DADU plan sets that move through plan review faster. Custom design buys flexibility at a 3-4x cost premium.Homeowner1-2 weeks · Free (decision)
   2. 2.2Schematic design + zoning compliance reviewYour designer produces 2-3 schematic options that meet Title 33.205, fit on the surveyed lot, and respect setbacks, height, and tree zones. You pick one.Designer, Architect3-5 weeks · Included in designer fee
   3. 3 in parallel
      2.3Energy-code path: prescriptive vs. performanceThe Oregon Energy Efficiency Specialty Code (OEESC) sets the rules. Pick the path early — it drives wall assembly, windows, and HVAC choices.Designer, Energy consultant1-2 weeks · Included in design or +$1,500 for performance modeling2.4Stormwater management plan (BES SIM)Any new impervious area triggers BES's Stormwater Management Manual. Most DADUs use the Simplified Approach — a drywell, infiltration planter, or rain garden does the job.Designer, Civil eng., Bureau of Environmental Services2-3 weeks · $1,500-$4,0002.5MEP plan coordinationMechanical, electrical, and plumbing layouts get confirmed against the architectural plan. Catches collisions before framing instead of after.Designer, Electrician, Plumber, HVAC contractor2-3 weeks · Included in design
4. Phase 3

   Permits

   Submit through DevHub, work through comments across 5-8 disciplines, and clear SDCs. Clean submittals usually wrap in 1-2 correction rounds.

   3-6 months·~$2,000-$5,000 (with SDC waiver) to $20,000-$30,000 (full SDCs)·5 steps
   1. 3.1Pre-application conference (optional but recommended)A PP&D meeting where reviewers across disciplines flag issues before you submit. $300-$600 and worth it on any tricky lot.Homeowner, Designer, PP&D2-4 weeks (scheduling) + 1 hour (meeting) · $300-$600
   2. 3.2Submit Residential Permit via DevHubOnline submittal through Portland's permit portal. You pay the plan-check fee at submittal; SDCs come later.Homeowner, Designer, PP&D1 day (submission) + 1-2 weeks (intake completeness check) · $1,200-$2,500 (plan check fee)
   3. 2 in parallel
      3.3Plan review (multiple disciplines)PP&D reviewers across 5-8 disciplines mark up your plans. You respond with revisions until everyone clears. This is the longest part of the permit phase and the part you have the most control over.Designer, PP&D8-16 weeks for first round; 4-8 weeks per revision · Included in plan check fee3.4Title 11 tree review (if triggered)Urban Forestry reviews the project against the tree code. You may need a revised footprint, a root-protection plan, or mitigation plantings.Urban Forestry, Arborist4-8 weeks (parallel to plan review) · $500-$2,500 in mitigation if removal required
   4. 3.5Pay SDCs (or finalize the waiver / exemption)Once plans clear, the SDCs you estimated back at 0.2 come due — or the ADU waiver / 2025-2028 exemption gets finalized and the bill drops to near zero. Either way, this gates permit issuance.Homeowner, Bureau of Environmental Services, Portland Water Bureau, PBOT1-2 weeks · ~$0 (with waiver/exemption) to ~$18,000+ (full rate)
5. Phase 4

   Bid and contract

   Permit in hand, you solicit bids from CCB-licensed contractors, normalize the apples-to-oranges responses, and sign with cooling-off-period protections.

   4-8 weeks·Included in build cost·3 steps
   1. 4.1Verify Oregon CCB licenses for everyone you ask to bidConfirm every GC, electrician, plumber, and mechanical sub on your bid list holds an active CCB license with the right endorsement, current bond, and current insurance. About 30 minutes on the state portal.Homeowner, Oregon CCB30 min per contractor · Free
   2. 4.2Solicit 3-5 GC bids from a normalized scopeSend the same plans and the same scope to 3-5 GCs. Normalized scope is the only way to compare apples to apples — otherwise you're comparing different houses.Homeowner, General contractor3-5 weeks · Free (some GCs charge for detailed estimates)
   3. 4.3Review bids, negotiate, draft contractPick the bid, negotiate scope and schedule, draft a contract. Oregon law gives residential clients a 3-day right of rescission, so you have a window to walk back if needed.Homeowner, General contractor, Attorney2-4 weeks · $1,500-$4,000 (attorney review)
6. Phase 5

   Build

   Construction starts once the permit issues and the contract's signed. 6-9 months is typical for a Portland DADU; weather and inspector availability are the main wall-clock variables.

   6-9 months·$300,000-$475,000·7 steps
   1. 5.1Demo, erosion control, tree protection, siteworkTree-protection fencing goes up first, then erosion control, then any demo. Inspectors check the sequence — get it out of order and you can stop work yourself.General contractor, PP&D, Bureau of Environmental Services, Urban Forestry1-3 weeks · $8,000-$25,000
   2. 5.2FoundationExcavate, form, place rebar, pour. Inspectors check rebar before the pour and verify final dimensions after.General contractor, PP&D2-4 weeks · $25,000-$45,000
   3. 5.3Framing + sheathing + roofing dry-inWalls up, roof on, building dried in to weather. Framing inspection happens before any wall covering goes on — schedule it as soon as the framer's done.General contractor, PP&D4-7 weeks · $45,000-$70,000
   4. 2 in parallel
      5.4Plumbing, electrical, mechanical rough-insPipes, wires, and ducts go inside framed walls. Each trade has its own rough-in inspection before insulation. All of them have to pass before drywall.General contractor, Plumber, Electrician, HVAC contractor, PP&D3-5 weeks · $35,000-$60,0005.7Siding, exterior trim, landscape, hardscapeThe final exterior look. Often runs in parallel with interior finishes, weather permitting.General contractor3-6 weeks · $30,000-$60,000
   5. 5.5Insulation + drywallInsulation goes in (with an insulation inspection), then drywall hangs and finishes. The building is now interior-ready.General contractor3-5 weeks · $18,000-$30,000
   6. 5.6Cabinets, flooring, tile, fixtures, paintAll your visible interior surfaces installed and finished. The longest build stage and the widest cost range — selections can swing 2-3x on the same DADU.General contractor6-10 weeks · $60,000-$120,000
7. Phase 6

   Energize and occupy

   Final inspections, utility energization, certificate of occupancy, and the rental decision (long-term, mid-term, or restricted short-term).

   3-6 weeks·$1,500-$4,000·5 steps
   1. 6.1Final inspections (all disciplines)Every discipline that did rough-in returns for final. All have to pass before the certificate of occupancy issues.General contractor, PP&D1-3 weeks (calendar) · Included in permit fee
   2. 6.2PGE service energizationPGE sets the meter and energizes the service. You schedule this with PGE separately from the city inspection — and the queue can be 2-6 weeks.Portland General Electric, General contractor2-6 weeks (lead time) · Included in PGE service fee
   3. 6.3Certificate of OccupancyPP&D issues the COO once all finals pass. It's your legal authorization to occupy the unit, and you've already done the hard part.PP&D, Homeowner1 week (after finals) · Included in permit fee
   4. 2 in parallel
      6.4Address assignment, 911, and recordsYour DADU gets its own address (something like 1234 1/2 NE Some St). Update USPS, 911, and county records so it shows up in the systems that matter.Homeowner, PP&D, Multnomah County1-2 weeks · Free6.5Rental decision: long-term, mid-term, or short-termPick the legal rental path that fits your setup — long-term, mid-term, or owner-occupied short-term — and line up the licensing and tax registrations it requires.Homeowner, AttorneyDecision (timeline depends on path) · $0-$2,000