Design-Build ADU Contractor
Portland ADU Builder
Detached ADUs, garage & basement conversions, designed, permitted & built by one team. One contract, one builder accountable from first sketch to final inspection.
Woman-led design-build firm run by Deb Zsarko, serving Portland, OR and Vancouver, WA for over 30 years.
A Design-Build ADU Builder Serving Portland, Oregon
If you're comparing ADU builders in Portland, ask each one who owns the problem when the drawings, the permit desk, and the job site disagree. At Z Squared Holdings, the answer is we do. Your accessory dwelling unit stays with one team from the first feasibility walk, through design and City of Portland permitting, to final inspection.
Long-term rental, guest house, home office, or a place for a parent to live close by: whatever the unit is for, you get a design meant to serve your family for decades, not just to pass inspection.
ADU Types & Portland Cost Ranges
$200–$350 per square foot, depending on ADU type & site conditions
Detached ADUs
(DADUs)$180,000–$280,000
A backyard cottage built new from the foundation up. It costs the most, and it earns it back in privacy and rental appeal no conversion can match.
Garage Conversion ADUs
$90,000–$150,000
Your garage already gives you a foundation, walls, and a roof, which is why conversions cost far less. Older Portland lots with detached garages are prime candidates.
Basement ADUs
Varies by Condition
Many older Portland houses have full-height basements that convert well. Ceiling height, egress, and moisture set the cost, so we check all three before you spend a dollar on design.
Attached & Internal ADUs
Site-Dependent
An addition or converted space that shares a wall with the main house but has its own entrance and kitchen. Usually the right call when a parent or adult child moves in.
Our ADU Work
Portland ADU projects by Z Squared
Portland ADU Permits, Zoning & the SDC Waiver
Portland allows ADUs by right in residential zones under Title 33. No hearing, no neighbor sign-off. If your design meets code, the city has to issue the permit.
You'll never be the one deciphering a correction letter from the city. We run the zoning analysis, the submittal, the checksheet responses, and the inspections.
Key Rules to Know
sq ft max (or 75% of primary dwelling, whichever is less)
SDC waiver savings (for ADUs ≤ 800 sq ft, expiring 2026)
typical permit & plan-review fees including trade permits
Our Design-Build Process
Feasibility to final inspection
Feasibility
You get a straight answer before you spend anything: we walk the lot, check zoning and utility capacity, and tell you what's buildable and what it should cost.
Design
Plans built around how you'll actually use the unit, with finishes picked to fit the budget we set together at feasibility.
Permitting
We prepare the full City of Portland submittal and answer every plan-review comment until the permit is in your hand.
Construction
The crew that builds is the team that drew the plans, so nothing gets lost in a hand-off. Most projects run 10–15 months start to finish.
ADUs in Vancouver & Clark County
Most Portland ADU specialists stop at the state line. We don't. Z Squared Holdings holds contractor licenses in both Oregon (CCB #252663) and Washington (ZSQUASH758JT).
Own property in Vancouver, Camas, Ridgefield, or anywhere in Clark County? Same process: one team carries feasibility, design, permitting, and construction, with 30 years of experience behind it.
Portland ADU FAQs
Common questions answered
How much does it cost to build an ADU in Portland?
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Most detached ADUs in Portland run $180,000–$280,000, garage conversions $90,000–$150,000, and pricing overall lands between $200 and $350 per square foot. ADU type, utility connections, site access, and finish level move the number most. You get a realistic budget range at feasibility, before design costs you anything.
Do I need a permit to build an ADU in Portland, Oregon?
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Yes. Every Portland ADU needs a building permit plus trade permits for electrical, plumbing, and mechanical, with combined fees typically running $6,000–$10,000. The good news: ADUs are permitted by right in Portland's residential zones under Title 33, so there's no hearing and no neighbor approval. We handle the whole submittal and plan review for you.
How big can an ADU be in Portland?
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Up to 800 square feet, or 75% of the primary dwelling's size, whichever is less. For most Portland homes the 800-square-foot cap is the limit that matters, and it fits a one- or two-bedroom unit comfortably. Staying at or under 800 square feet also keeps you eligible for the city's SDC waiver.
Are SDC fees waived for ADUs in Portland, and when does the waiver expire?
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Yes. Portland waives system development charges (SDCs) for ADUs up to 800 square feet, a savings typically worth $15,000–$25,000 per project. The waiver is set to expire in 2026, so projects that enter design and permitting now are best placed to catch it. Know that taking the waiver limits short-term rental use of the unit for a period of years.
How long does it take to design, permit, and build an ADU in Portland?
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Most Portland ADU projects take roughly 10 to 15 months from the first design meeting to final inspection. Design takes a few months, city plan review a few more, and construction is the longest stretch. Because the same team handles all three, the project doesn't stall between phases.
Can I rent out my ADU in Portland, or use it for family?
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Yes. A Portland ADU can be a long-term rental, housing for family, guest quarters, or a home office, and nobody is required to live in the main house. The one caveat: ADUs built with the SDC waiver are barred from short-term rental use for a period of years. Many of our clients house a parent now and plan on rental income later.
Start with a Free ADU Feasibility Consultation
Tell us about your lot and what you want from it. We'll walk the site, check the zoning, and hand you a realistic budget and timeline before you commit to a thing.
The SDC waiver is scheduled to expire in 2026. Worth finding out what your lot can do while the savings are still on the table.
WHAT OUR CLIENTS ARE SAYING
DON'T JUST TAKE OUR WORD
Tamar Feinkind
Home Owner
I worked with Deb Zsarko twice, first to renovate a 1 bedroom condo – kitchen, flooring, and paint – and the second time to completely gut a 1500 sq ft house. Five years on, we feel lucky to have worked with Deb to redo our 1940 house. The work she does lasts, and she considered things in terms of aesthetics that we had never thought of. She works with top of the line people, as well. Mostly, she's a person of her word! And that's rare in this business.
Mae-Fay Koenig
Home Owner
Deb did an incredible job with our master bathroom and walk in closet remodel! She's pretty accurate with her estimates and timeline which is a rare thing to find. Deb has a wealth of knowledge and experience with all things related to home construction and remodels. If she was still local to us, we would have had her tackle our kitchen remodel as well. Highly recommend Deb to anyone who wants a stress free remodel!