Skip to main content Skip to content Portland ADU Builder · Now Booking 2026
Detached, attached, and garage-conversion ADUs by Portland’s design-build team. One firm from permit to certificate of occupancy. Now booking 2026 projects across the Portland metro. Review the City of Portland ADU permitting requirements before you begin.
Google rating
Oregon licensed
in Portland
Quick Cost Answer
Honest ranges, not single numbers. Unit pricing in Portland tracks five things: foundation type, utility connections, finish level, square footage, and whether the existing structure stays intact.
The real estimate comes after design. We sign a contract on a fixed price, not a guess. No surprise change orders unless you change the scope yourself.
New standalone build, 600 to 800 sq ft. Most full-scope projects: $300K to $385K.
Attached to the primary dwelling. Shared wall, separate entry, separate utilities.
Existing garage to living space. Reuses foundation and roof. 4 to 6 month build.
Basement or attic to living unit. Code-compliant egress, separate entry, full kitchen and bath.
Second primary dwelling on the same lot. Different rules from standard ADUs.
Itemized estimates within one business day · CCB #181942 · Free in-home consultation
Quick Answer
$350 to $550 /sq ft
Total project: $180K to $450K depending on type, finish level, and site work.
Detached. Garage conversions: 6 to 9 months total.
$1,800 to $2,800
Long-term lease, 2026 Portland market, 500 to 800 sq ft units.
Permitted, legally rentable unit vs. comparable home without one.
Our Approach
An accessory dwelling unit should earn its place in the lot before it earns its place in the code. We design every Portland home to read as part of the home, then build it to outlast the next two decades of city policy.
By Type
Every Portland unit falls into one of five briefs. Knowing which one fits your lot, budget, and goals shapes every later decision: foundation, utilities, code path, timeline. We start there.
Standalone backyard build. New foundation, separate utilities, 600 to 800 sq ft. The flagship Portland build. Most freedom, longest timeline.
Shares one wall with the primary dwelling. Separate entry, separate utilities, separate address. Faster than detached, closer to the home.
Existing garage to living space. Reuses foundation and roof. Lowest cost, fastest path to occupancy. Limited by the existing footprint.
Basement, attic, or finished bonus room into a code-compliant unit. Egress, ceiling height, separate entry, full kitchen and bath.
A second primary dwelling on the same lot under Portland’s RIP rules. Different code path from a standard unit. Maximizes lot value.
Choose Your ADU
Every lot is different. We design and build the type that fits your zoning, your budget, and the role you want the unit to play. Costs and timelines below reflect 2026 Portland projects.
Detached ADU
A separate backyard cottage, up to 800 sq ft. Best resale lift, easiest to rent, most privacy for owner and tenant.
$280K to $440K
10 to 14 mo
500 to 800 sq ft
$2,200 to $2,800
Attached ADU
Shares a wall with the main house but has its own entry, kitchen, and bath. Lower cost than detached because it shares roof, foundation, and utilities.
$210K to $340K
8 to 12 mo
500 to 800 sq ft
$1,900 to $2,400
Garage Conversion
Convert an existing detached or attached garage into a permitted unit. The shell is already there. You pay for systems, finishes, and code upgrades.
$180K to $260K
6 to 9 mo
350 to 600 sq ft
$1,800 to $2,200
Basement ADU
Full or partial basement converted into a separate dwelling. Requires egress, ceiling height, and waterproofing review. Best in pre-1960 Portland homes with daylight basements.
$160K to $240K
5 to 8 mo
500 to 900 sq ft
$1,800 to $2,400
The Math
The numbers below model a 600 sq ft detached unit in inner-Portland in 2026. Real projects vary. The pattern doesn’t.
— Step 01
$245K
600 sq ft detached at $410/sq ft. Includes design, permits, foundation, shell, finish, utility extension, and final inspection.
— Step 02
$2,400/mo
Long-term unfurnished lease, 2026 Portland market for a permitted detached unit. After 5 to 10 percent vacancy and operating costs.
— Step 03
~8.5 yrs
Pure cash recovery, ignoring appreciation and tax depreciation. Many owners refinance within 3 to 5 years to recapture equity.
— Step 04
+18%
Average inner-Portland comp lift for a permitted, legally rentable unit on a single lot. On a $750K home, that’s $135K of new equity at completion.
Modeled on inner-Portland 2026 comps. Your scenario will differ. · Ask for the full breakdown in your free consult.
Featured Project
The rent covers our property tax increase and half the mortgage. Eight months from contract to keys, no change orders. Their PM ran the city and the trades so we never had to.
720 sq ft
$275K
$2,400/mo
2026 Portland ADU Code
Portland’s ADU code shifted in three meaningful ways at the start of 2026. Knowing them is the difference between a project that pencils and one that stalls.
SDC fee waivers
Portland still waives System Development Charges on the first unit per lot, provided the unit is not used as a short-term rental during the first 10 years. The waiver carries a deed restriction that transfers with sale, so structure your plan accordingly.
$10K to $20K saved
Pre-approved plan sets
The Bureau of Development Services now offers a library of pre-approved plan sets that bypass full structural review. We use them when they fit; we draw custom when site or owner needs warrant. The trade-off is design flexibility versus 6 to 8 weeks off the timeline.
6 to 8 weeks faster
Two ADUs per lot
Most Portland residential zones now allow two ADUs per lot: one attached and one detached, or one converted basement plus one detached cottage. This is the rule that turned single-family lots into small income-producing properties in 2026.
Up to 2 ADUs allowed
The Process
We walk the lot together. Look at setbacks, utilities, sight lines, the realistic path to a code-compliant unit. No pressure, no quote pulled from thin air.
The full cost breakdown delivered within one business day. Foundation, framing, utilities, finishes, permits. No mystery line items.
Anna leads design. Site plan, elevations, floor plan, fixture and finish selections in the showroom. We lock the spec before any permit is filed.
Tyrell submits to Bureau of Development Services, manages corrections, and clears land use review. We own the timeline through every revision request.
Site prep, foundation, framing, utilities, rough-in, drywall, finish carpentry, paint, fixtures. One PM, one site, one accountable team. Daily clean-up, weekly walks.
Final inspections clear. Punch list resolved. Certificate of occupancy issued. One-year craftsmanship warranty in writing. We circle back at six months to check finishes.
Cost Guide
Know the numbers before you build. Our Portland ADU cost guide breaks down foundation, framing, systems, and finishes so you can size your budget with confidence – tailored to your lot and the unit you have in mind.
Featured Project
“We had walked four other contractors through the backyard before WCG. They were the only firm that drew us a real site plan in the first meeting. Eight months later we had a finished unit and our daughter’s family in the back. Quietly excellent.”
Five recent units across Portland metro. Sizes, neighborhoods, and finish levels you can stand inside before deciding.
Frequently Asked
The seven questions Portland homeowners ask us most often before signing a build. Direct answers, no marketing.
Give us a call. We’d rather answer it directly than make you scroll.
A new detached ADU in Portland costs $250K to $450K in 2026, with most 600 to 800 sq ft builds landing between $300K and $385K. Attached ADUs run $200K to $350K. Garage conversions are $150K to $250K. Interior conversions (basement or attic to ADU) start at $120K. The range tracks foundation type, utilities, finish level, and whether the existing structure stays intact.
A detached ADU takes 7 to 10 months from permit submission to certificate of occupancy. The design and selections phase runs 6 to 10 weeks, permit review another 8 to 14 weeks, and construction 16 to 22 weeks. Garage conversions move faster: typically 4 to 6 months total. Permit timelines depend on the bureau and the complexity of the site, especially for projects on RIP-affected lots.
Yes, every ADU in Portland requires a building permit and most require land use review. Under Portland’s Residential Infill Project (RIP), most R-zoned lots can have one ADU per primary dwelling, with reduced parking and setback requirements. Two-on-one projects (where a second primary dwelling is built) follow different rules. We pull every required permit, manage land use review, and own the timeline through Bureau of Development Services.
Portland ADUs are capped at 800 square feet OR 75% of the primary dwelling, whichever is less. Detached ADUs typically max out at 800 sq ft on standard R-zoned lots. Attached ADUs and interior conversions follow the same total cap but can be configured across multiple floors. Garage conversions are limited by the existing footprint unless you add a second story (which adds 4 to 6 weeks to the design phase).
Yes, with restrictions. Portland allows short-term rentals (Type A and Type B) in ADUs, but you must register the unit with the city, occupy the primary dwelling for at least 270 nights per year, and meet life-safety code (smoke alarms, egress, hardwired CO detection). Long-term rentals have fewer restrictions. We design every ADU to meet both short-term and long-term rental code from day one, so the option stays open.
A detached ADU is a new standalone structure built from the foundation up, typically 600 to 800 sq ft, with its own utilities, kitchen, bathroom, and entry. A garage conversion takes an existing detached or attached garage and converts it into living space, reusing the foundation and roof. Detached costs $250K to $450K and takes 7 to 10 months. Garage conversion costs $150K to $250K and takes 4 to 6 months. The right choice depends on whether you need the garage for parking, the condition of the existing structure, and your budget.
Yes, design-build is the only way we work. The team includes a designer, a structural consultant, a permits coordinator, a project manager, and the trades. Anna Woodland leads design, Tyrell manages the build, and Tyrone signs every estimate. There are no handoffs between architect, designer, and contractor. One firm, one contract, one accountable team from the first sketch to the final inspection.
Service Areas
From the Pearl District to Lake Oswego, Beaverton to Sellwood. Local zoning, local lot conditions, local crews on every project.
Keep Exploring
Ready When You Are
Free in-home consultation. Itemized estimate within one business day. Now booking 2026 projects across the Portland metro.
