ADU BUILDER IN PORTLAND & VANCOUVER
Detached ADUs, garage conversions, and attached in-law suites — designed, permitted, and built for you.
Quick Answer
Masters Construction builds ADUs in Portland and Vancouver, WA — detached units, garage conversions, and attached in-law suites. Pricing is set after a site walk because utilities, access, and lot conditions drive the number. Licensed in Oregon (CCB #248237) and Washington.
An accessory dwelling unit adds rental income, a guest house for family, or a future downsizing option on the property you already own. As ADU builders licensed in both Oregon and Washington, we handle design and construction across the Portland metro and Clark County.
Every project starts with a zoning and setback review so you know what is buildable before design begins. From there the backyard cottage or in-law suite is engineered, permitted, and built as a complete small home — foundation, envelope, kitchen, bath, and utility connections.
Our build process keeps the unit inside current building codes for egress, energy, fire separation, and utility metering, so it passes inspection the first time.
Because we work design-build, the drawings and the price come from the same team. That removes the gap between a plan set and what a builder will actually charge to build it.
Scope of Work
What’s Included
Zoning & setback review
What your lot allows, confirmed before design starts.
Detached ADUs
Standalone backyard cottages built as complete small homes.
Attached ADUs & in-law suites
Independent living space connected to the main house.
Garage-to-ADU conversions
Existing structures insulated, re-framed, and brought to code.
Basement ADUs
Egress, ceiling height, and separate entry resolved properly.
Utility connections
Water, sewer, power, and gas routed, metered, and permitted.
Permits in OR & WA
Submittal and inspections handled on both sides of the river.
Why build an ADU in Portland
A backyard cottage is one of the few projects that adds living space, monthly income, and long-term flexibility to a lot you already own. Working as accessory dwelling unit builders Portland and Vancouver homeowners hire for complete design-build projects, we hear the same reasons come up again and again.
Added property value
A permitted, code-compliant unit adds finished square footage and documented rental potential, both of which appraisers and buyers can price. Gains are strongest where an accessory dwelling unit Portland Oregon appraisers can compare against recent sales of similar homes with units, so we review comparable sales in your neighborhood before you commit to a budget.
Rental income
A detached ADU in Portland commonly rents in the range of $1,500 to $2,500 per month, with smaller studio units at the lower end and newer, well-located one-bedrooms at the higher end. These figures move with the rental market — confirm them against current local listings before you model your return.
Long-term rentals are straightforward on most lots. Short-term rental use is regulated separately and carries its own permit, which we flag during the site walk.
Flexible living for family, guests or aging parents
An ADU keeps adult children, guests, or aging parents close while preserving privacy on both sides of the property. Wide doors, zero-threshold entries, and a full bathroom can be planned in from the first sketch, and the same details carry through the main house — see our aging-in-place remodeling work for how those decisions come together.
ADU vs tiny home in Portland
The city of Portland ADU standards treat a backyard cottage as a real dwelling: permanent foundation, connected utilities, and full inspections. A tiny home on wheels is regulated differently and generally cannot be permitted as an ADU on a residential lot.
An ADU permit Portland reviewers approve the first time depends on complete drawings — zoning, setbacks, utility connections, and egress documented up front. We prepare that package and carry it through review.
Portland ADU rules in plain English
Portland allows an accessory dwelling unit on most single-family lots. Size is capped — generally 800 square feet or 75 percent of the main house, whichever is less. Detached units also have height and setback limits that vary by zone.
There is no owner-occupancy requirement in Portland. You do not have to live on the property to build or rent the unit. Short-term rental use is regulated separately and has its own permit.
System development charges are the other cost to watch. Portland has waived or reduced SDCs for qualifying ADUs at various points, and the terms change. We confirm the current SDC status with the city for your address before pricing, and you should treat any figure you read online as out of date until the city confirms it.
We check zoning, setbacks, tree code, and lot coverage during the site walk. Confirm current rules with the City of Portland, since code updates land regularly.
Vancouver WA and Clark County ADU rules
Vancouver allows ADUs on most single-family lots, both attached and detached. Size limits are generally more generous than Portland's, and garage conversions are common where the existing slab and walls can be brought to code.
Unincorporated Clark County applies its own standards through Community Development, including septic and well capacity where there is no city sewer. That review can add weeks, so we start it early.
Fire separation, egress, parking, and utility metering are the usual review items on both sides of the river. We prepare the drawings and submittals and carry the project through inspections. Confirm current rules with the City of Vancouver or Clark County before you commit to a size.
Garage conversion vs detached ADU: which is right for your lot
Both options add a legal second unit, but they differ in cost, schedule and how renters see them. The right choice usually depends on whether your existing garage is sound and whether your lot has room to build new.
A garage conversion reuses the slab, walls and roof, so it is faster and costs less. A detached ADU is built from the ground up, which means more design freedom and better long-term rental appeal.
| Factor | Garage conversion | Detached ADU |
|---|---|---|
| Typical cost | Lower — reuses slab, walls and roof | Higher — new foundation and full structure |
| Construction timeline | About 3 to 5 months | About 6 to 10 months |
| Permits | Change of use, energy and egress review | Full new-structure review, setbacks and utilities |
| Rental appeal | Good; ceiling height and light can be limits | Strong; built as a complete small home |
Financing an ADU
Most homeowners pay for an ADU with one of three common tools. Each works differently, and a lender or financial advisor can tell you which fits your situation.
The figures and terms depend on your lender, your equity and current rates. We provide drawings, a fixed price and a schedule, which lenders typically ask for before approving a loan.
- Home equity line of credit (HELOC) — a revolving line secured by your house. You draw funds as the project moves and pay interest on what you use.
- Cash-out refinance — replaces your current mortgage with a larger one and pays out the difference in cash at closing.
- Construction loan — a short-term loan paid out in stages as work is inspected, often converting to a long-term mortgage when the unit is finished.
How to choose among the best ADU builders in the Portland area
Start with a builder who can explain what your particular lot allows, not a generic square-foot price. Ask who checks zoning, setbacks, trees, access and utility capacity before a plan is sold. In Vancouver or unincorporated Clark County, confirm that the team understands which jurisdiction reviews the address.
Compare proposals against the same scope. A low construction number may leave out utility trenching, site work, design, permit fees, appliances or landscaping. Ask for a line-item estimate and a written process for changes discovered after excavation or demolition.
Licensing matters on both sides of the river: any ADU contractor Portland homeowners hire must hold an Oregon CCB license, and Clark County work requires Washington registration as well.
Request examples of permitted ADUs similar to yours and references you can speak with. Confirm licensing and insurance, who manages the site, how often you receive updates, and what the workmanship warranty covers. A realistic schedule should distinguish design, approvals, long-lead orders and construction rather than promising one start-to-finish date.
- Verify the builder's license, insurance and relevant ADU references.
- Ask for an address-specific feasibility check and utility plan.
- Compare complete written scopes, allowances and change-order terms.
- Review the permit path, construction schedule and warranty in writing.
ADU plans and layouts
A compact studio may fit in roughly 300 to 450 square feet, with a single living and sleeping zone, kitchenette and bath. It works best when storage and daylight are planned into the floor plan rather than added after framing. Local minimums, maximums and lot rules still need an address-specific check.
A one-bedroom layout often uses about 450 to 650 square feet. Separating the bedroom from the living room gives guests or renters more privacy without requiring a large footprint. A two-bedroom plan may need around 650 to 800 square feet or more, depending on the jurisdiction, and benefits from careful circulation so hallways do not consume the floor area.
Garage conversions inherit the dimensions of the existing shell, but the final plan must accommodate insulation, a code-compliant bathroom, kitchen, egress and mechanical space. We check slab condition, ceiling height and the placement of doors before deciding whether the shell actually saves money. For every option, place windows and entries with the main house's privacy and outdoor paths in mind.
Energy-efficient ADU design
Energy choices cost the least when they are made during design rather than after framing. We insulate the envelope to current code, size a ductless heat pump for the compact floor plan, and rough in conduit for future solar so you keep the option open without committing to panels now.
- Studio: one flexible room with built-in storage and a separate bath.
- One-bedroom: distinct sleeping and living spaces in a modest footprint.
- Two-bedroom: more privacy, but a larger footprint and tighter lot constraints.
- Garage conversion: layout shaped by the shell, slab and existing openings.
How It Works
Our Process
- 1
Consultation & site walk
We walk the home with you, measure the existing structure, and talk through goals, budget range, and timing before anything is drawn.
- 2
Design & engineering
Our in-house studio produces plans and 3D views, and our structural team engineers the framing, foundations, and systems behind them.
- 3
Permits & pricing
We prepare and submit the permit package, answer plan-review comments, and lock a detailed, line-item price against the approved set.
- 4
Build & walkthrough
One Masters project lead runs the trades, schedules inspections, and finishes with a punch walkthrough before handing the space back.
From the Field
Recent Work
Where We Build
Areas We Serve
See every neighborhood we build in on our Portland Metro service areas map.
Client Reviews
What clients say
A new room was built along with deck and patio, in place of covered deck. Chris and his team always responded and stayed on budget, went above and beyond with meeting our needs, with quality finishes on all levels. Simply couldn't be happier with the outcome. Definitely recommend them.
Sreepallavi T.
Portland, OR · Room addition, deck and patio
Finally got around to doing the guest bathroom reno after the master bath last summer and I could not be happy enough! Our previous contractor had changed states, but a friend referred Masters and our remodel was perfect from start to finish.
Denis M.
Portland, OR · Primary and guest bathroom remodels
I recently had my bathroom remodeled by Masters Construction, and I couldn't be happier with the results! They did an incredible job communicating each step of the process, ensuring I was always in the loop about timelines and what to expect.
Zack Turner
Portland, OR · Bathroom remodel
Frequently Asked
Accessory Dwelling Unit Construction FAQs
What Portland and Vancouver homeowners ask before they begin.
ADUs price as new construction and follow the same $400–$700 per square foot addition range, though utility runs, site access, and setbacks move the number. We give firm pricing after the site walk.
See our Portland remodeling cost guide for detailed ranges.
Start Your ADU Project
Tell us about the home and we’ll walk the site, talk through scope, and give you a realistic range — no obligation.
CCB #248237 · Licensed in Oregon & Washington