ADU Builder
Portland’s Master Certified ADU Builder. 20 years, 4.9 on Houzz, top 2% on Buildzoom.
An ADU is a second home on the land you already own, and there are three real ways to build one: a detached new build, a garage conversion, or a basement conversion. Each fits a different lot, budget, and timeline, and the right choice depends as much on your property as on your goal.
C&K Custom Remodeling builds all three as a design-build firm, which means feasibility, design, permits, structural, and construction are handled in-house, so the project does not stall between phases. A good ADU does not look like an afterthought in the back yard. It looks like it belongs to the property.
Why Portland Families Build ADUs
Before the types and the rules, it helps to start with who actually builds an ADU and why. The reasons we hear most:
- An aging parent moving in who needs single-level living, a private entrance, and a bathroom built for the long haul.
- An adult child returning home or finishing college, who needs their own space without leaving the family property.
- Long-term rental income on a property the homeowner already loves and does not want to leave.
- A home office, studio, or guest house with a private entrance and full separation from the main house.
- Future flexibility: a rental today, an in-law suite in five years, a primary residence in twenty.
ADU Examples
Every ADU starts with a different goal. Here are three that came out very different.
Detached ADU: Ardenwald-Johnson Creek
Detached new-build DADU, 800 square feet, two stories
What it is: a freestanding second home built new on the property, with its own foundation, kitchen, bath, and private entrance. A DADU offers the most separation from the main house and the strongest long-term rental potential, and because everything is built from the ground up, it can be designed around exactly how it will be used.
The project: in the Ardenwald-Johnson Creek neighborhood, we built this 800 square foot detached ADU new, across two stories from foundation to finish. A vaulted ceiling with skylights and clerestory windows carries daylight deep into the upper living space, while a full galley kitchen, a main bath, and a separate powder room make it a complete, self-sufficient home. Rooftop solar and warm vertical siding tie it to the property and the neighborhood, the kind of second home that reads as built-for rather than added-on.
Wood Village Garage Conversion
Existing garage converted to a fully accessible apartment
What it is: An existing garage rebuilt into a complete, self-contained living space, with its own kitchen, bath, and entrance. A garage conversion keeps cost down and preserves the yard, because the foundation and structure are already there. It is often the most direct path to a second dwelling when the existing building is sound.
In Wood Village, we converted a garage into a fully accessible apartment so the homeowner could stay on the property rather than sell. The bathroom was built around how it would be used, with a curbless roll-in shower, a fold-down teak bench, grab bars, and a linear drain set flush to the floor. Wide clearances and comfort-height storage carry that same thinking through the space. The result let our home owner with disabilities keep their home and an independence that selling would have cost them.
Hawthorne Basement ADU
Basement finished as a separate dwelling, 750 square feet
What it is: a separate dwelling finished within the home’s existing basement, with its own entrance, egress windows, kitchen, and bath. A basement ADU adds a full second unit without changing the home’s exterior, which makes it a strong fit when the goal is in-law or adult-child living and the basement has the ceiling height to carry it.
The project: in the Hawthorne neighborhood, we finished this 750 square foot basement into a complete, light-filled apartment. An open plan holds a king bedroom, a separate sitting and dining area, and built-in bookshelves that divide the spaces without closing them in, while daylight windows keep it from ever reading as a basement. A double-vanity bath in marble and brass gives it the finish level of the main house, fully a part of it rather than a step below.
Talk to C&K About Your ADU
Why Homeowners Choose C&K Custom Remodeling
An ADU runs through feasibility, design, permitting, structural work, and construction, and the projects that go smoothly are the ones where a single team owns all of it, accountable to one timeline and one budget.
- Master Certified credentials: Lloyd Martindale holds both the Master Certified Remodeler (MCR) and Master Certified Kitchen & Bath Remodeler (MCKBR) designations, held by fewer than 1% of contractors nationwide
- Design-build: feasibility, design, permits, structural, and construction in-house, so the project does not stall between phases.
- Over 20 years in Portland-area neighborhoods, from older Craftsman lots to Lake Oswego and West Linn subdivisions.
- Long-tenured carpenters and framing crews, not a rotating subcontractor crew.
- ADUs designed to read as part of the property: matched rooflines, matched siding, matched window proportions, not a shed in the back yard.
- A track record you can verify: two decades of 5-star reviews from Portland-area homeowners and a Houzz rating of 4.9 out of 5, and Buildzoom score that places us in the top 2% of Oregon contractors.
ADU Cost in Portland
Think of an ADU as an investment rather than a price, because what it costs depends on type, lot conditions, and finish level. A garage conversion that reuses a sound foundation and roof sits at one end. A detached new build, where foundation, framing, roof, and systems all come from scratch, sits at the higher end of cost per square foot.
Typical investment ranges at C&K, by type:
- Garage Conversion ADU: $150,000–$300,000. The lowest cost per square foot when the existing structure has a sound foundation and roof.
- Basement Conversion ADU: $250,000–$400,000. Driven by egress window cuts, plumbing for a new kitchen and bath, and whether the basement is already conditioned.
- Detached New-Build DADU: $350,000+. Higher per square foot because foundation, framing, roof, and systems all come from scratch.
- Premium Custom ADU: $400,000+. High-end finishes throughout, often comparable per square foot to a custom primary home.
Soft costs fit inside the budget rather than arriving as surprises: design fees, structural engineering, surveying, geotechnical work where required, permits, and System Development Charges.
Why an ADU Is One of the Best Property Investments
Built on land you already own, an ADU is one of the strongest property investments available to a Portland homeowner.
- Long-term rental income on a property the family already lives on, with no second mortgage and no second commute.
- Multi-generational flexibility: housing aging parents or adult children without selling and buying again
- A lift in property value: a permitted, well-built ADU adds livable square footage that appraisers and buyers both recognize.
The 6-Step Process
Every ADU follows the same path, so you always know what is next.
- Feasibility: zoning, setbacks, lot coverage, sewer and water capacity, and SDC estimates, before any design hours are spent.
- Concept design: footprint options, exterior direction, and an interior layout matched to who will live in it and how it ties to the main house.
- Permit drawings: full architectural, structural, mechanical, electrical, and plumbing drawings submitted to BDS.
- Permit review and revisions: handling city plan-review comments, structural revisions, and SDC sign-off.
- Construction: foundation for a DADU, demo and rebuild for a garage, or interior buildout for a basement, with a dedicated project manager and weekly updates.
- Utility tie-ins and final walkthrough: separate sewer lateral if required, water meter or shared service, electrical sub-panel, final inspections, and certificate of occupancy.
See What C&K Can Do With Your Property
Types of ADUs We Build
Not every property fits every ADU type. The right one depends on your lot, your budget, and your goal. A quick guide to the four we build:
- Detached ADU (DADU): a freestanding new build, typically 600 to 800 square feet with its own kitchen and bath. Best when the lot has room, you want visible separation, and long-term rental income is on the table.
- Garage Conversion ADU: an existing attached or detached garage rebuilt as livable space. Best when the structure is sound and you want to keep cost down and preserve yard space.
- Basement Conversion ADU: a daylight or full basement with a separate entrance, egress windows, kitchen, and bath, finished to code. Best when the home has the ceiling height and the goal is in-law or adult-child living without changing the exterior.
- Bump-Out / Attached ADU: a new addition designed as an internal ADU with its own entrance and full kitchen. Best when zoning blocks a DADU but the lot still has room for an addition.
Portland ADU Rules and Lot Feasibility
Feasibility comes before design hours because the rules vary by city and decide what is buildable on your lot in the first place. The factors that shape it:
- Portland zoning (R5 / R2.5): up to two ADUs per lot in most residential zones, no owner-occupancy requirement, an 800 square foot footprint cap on DADUs, and a 25 foot height limit.
- Setbacks, lot coverage, and tree preservation that decide whether a DADU even fits on the lot.
- System Development Charges (SDCs) and how they shape the budget for sewer, water, and parks.
- Lake Oswego, West Linn, and Tigard rules: more restrictive than Portland on setbacks, design review, and ADU count per lot.
- Historic and design-review overlays in older Portland neighborhoods that add a design-review step before permits.
FAQs About ADUs
How many ADUs can I build on my Portland lot?
In most Portland residential zones, up to two ADUs per lot, often a detached unit plus an interior or basement unit. The exact count depends on your zone and lot, which we confirm during feasibility.
Do I have to live on the property to rent out my ADU?
Portland does not impose an owner-occupancy requirement to rent an ADU. Surrounding cities can differ, so we verify the rule for your jurisdiction before design.
What is the difference between a DADU, a garage conversion, and a basement ADU?
A DADU is a freestanding new building. A garage conversion rebuilds an existing garage as living space. A basement ADU finishes a separate unit inside the existing home with its own entrance. Lot, budget, and goal usually point to one of the three.
How long does a Portland ADU take from design through certificate of occupancy?
Most run several months, with feasibility and design up front, then permit review, then construction. Plan review and SDC sign-off are often the least predictable stretch, which is why we start there rather than at design.
What are System Development Charges, and how much should I budget?
SDCs are city fees for connecting to sewer, water, and parks infrastructure. They vary by jurisdiction and project, and we include an SDC estimate in the feasibility step so the number is in your budget from the start.
Service Area
We build ADUs across the Portland metro, with working familiarity of the city-by-city rules and lot conditions that shape what is buildable in each.
Portland · Lake Oswego · West Linn · Dunthorpe · NW Portland · West Hills · Beaverton · Tigard · Tualatin
See how C&K can help with your ADU project
