ADU Construction in Portland, OR

Detached Backyard Cottages. Attached & Basement Conversions. Garage Conversions. Design & Permitting Handled. One Owner-Supervised Contractor. Licensed OR #241979 | WA #VRESHCL776ND.

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An accessory dwelling unit is a small, self-contained second home on your property, with its own kitchen, bath, and entrance. Portland is one of the most ADU-friendly cities in the country, and homeowners build them for rental income, for aging parents or adult kids, for a home office or studio, and for the value they add to a property. An ADU is also a full building project with real complexity: zoning and setbacks, utility connections, structural work, and a multi-step permit process. VResh builds ADUs the way we build everything, with the owner on the project and one contractor accountable for the whole thing, from the first design conversation through the final inspection.

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01.

Owner-Supervised Always

Vlad is on every project, start to finish

02.

Detached, Attached & Garage ADUs

All three types under one contractor

03.

Design & Permitting Handled

Managed with our design and architecture partner

04.

Built as One Project

Structural, systems, and finishes coordinated, not handed off

05.

Licensed & Insured

OR #241979 | WA #VRESHCL776ND

06.

Written Estimates Only

Scope and cost confirmed before any work begins

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(503) 272-6436 — Call or Text, Available 24/7

We answer calls and texts at any hour. For storm damage, active leaks, or structural emergencies, calling directly is the fastest path to a response.

Three Ways to Add an ADU: Detached, Attached, and Garage Conversion

There are three main ways to create an ADU in Portland, and the right one depends on your lot, your budget, and how you plan to use the space. We help you weigh them at the first conversation.

Detached ADU

A standalone structure in the backyard, sometimes called a backyard cottage or DADU. It offers the most privacy and flexibility and the highest resale appeal, and it is the most involved and most expensive of the three because it needs its own foundation, structure, and utility runs. It is the classic choice for rental income or a private in-law suite.

Attached or interior ADU

An ADU created within or added onto the existing house, including a basement conversion into a separate unit. It reuses the home's structure and is often more economical than a detached build, while giving a tenant or family member a private, self-contained space. A basement ADU is a popular version; see our basement finishing page for that groundwork.

Garage conversion ADU

Converting an existing detached garage or accessory structure into living space. It reuses a footprint and foundation you already have, which can make it one of the more cost-effective paths to a detached-feeling unit, provided the existing structure is sound and can be brought up to code for habitation.

Portland ADU Rules, in Plain Terms

Portland actively encourages ADUs, but they come with rules, and the details change, so we confirm the current requirements for your property during design. In general terms:

We handle the code side as part of the project, designing to what your lot allows and steering the plans through the permit process so the finished ADU is legal and inspected.

  • Size: an ADU is capped at roughly 800 square feet or a share of the primary home's floor area, whichever is smaller, and it must be smaller than the main house.
  • Zoning and siting: setbacks, height, and lot-coverage limits apply, and they affect where and how large a detached ADU can be.
  • Utilities: the ADU needs water, sewer, and electrical service, which for a detached unit usually means trenching and new connections.
  • Permits: an ADU goes through a full building permit with structural, electrical, plumbing, and mechanical review and inspections.

Why Portland Homeowners Build ADUs

An ADU is one of the few home projects that can pay you back every month. The most common reasons homeowners build them:

  • Rental income: a long-term rental unit that helps carry the mortgage or funds the next project.
  • Multigenerational living: a private, accessible home for aging parents or a space for adult kids, close but separate.
  • Work and hobbies: a quiet home office, studio, or guest quarters detached from the main house.
  • Property value: a permitted, self-contained second unit adds meaningful resale value in Portland's market.

What This Means for You

We design the ADU around your goal, whether that is maximizing rentable space, building for accessibility, or matching the character of your main home.

How an ADU Project Works

An ADU is a full building project, and the early planning is what keeps it on budget and on schedule. Here is the sequence.

#
Item
What We Do — And Why It Matters
1
Feasibility and design
We look at your lot, zoning, and utilities to confirm what is possible, then work with our design and architecture partner to design an ADU that fits the rules and your goals. You get a written estimate with scope and cost before the build is committed.
2
Permitting
Our design partner prepares and submits the plans, and we steer the project through Portland's permit process together, responding to plan-review comments so it is cleared to build.
3
Site work and foundation
For a detached ADU, we handle site preparation, the foundation, and utility trenching. For conversions, we complete demolition and any structural upgrades the existing building needs for habitation.
4
Framing, systems, and shell
We frame the unit and coordinate the licensed electrical, plumbing, and mechanical rough-ins, then close in the shell with roofing, siding, windows, and doors, with inspections along the way.
5
Insulation, drywall, and finishes
We insulate, drywall, and finish the interior with flooring, trim, paint, a kitchen, and a bathroom, building a complete, move-in-ready home.
6
Final inspection and handover
We complete the final inspections and any certificate of occupancy steps, walk the finished ADU with you, and close out any punch-list items before handover. Photo documentation: we photograph the foundation, framing, and rough-ins so there is a record of the structural and hidden work for your file and warranty.

What's Included in an ADU Project

Scope depends on the ADU type and your lot, and a full ADU build includes the items below. Coordinated trades and conditional work are noted so there are no surprises on the estimate. Every lot and ADU is different. We scope yours around zoning, utilities, and your goals, and tell you honestly what the site allows before design gets far.

Scope item
Status
What it means
Feasibility & design
Included
Lot/zoning/utility review; design with our architecture partner
Permitting
Included
Plan submittal and plan-review coordination
Site prep & foundation
Included
For detached ADUs; conversions handle existing slab/foundation
Utility connections
Included/As needed
Water, sewer, and electrical; trenching for detached units
Structural upgrades
As needed
Bringing a garage or basement up to code for habitation
Framing & shell
Included
Framing, roofing, siding, windows, and doors
Electrical / plumbing / mechanical
Coordinated
Licensed trades; heating typically a ductless mini-split
Insulation, drywall & interior finishes
Included
Flooring, trim, paint, and lighting
Kitchen & bathroom
Included
A complete, self-contained unit
Final inspections & certificate of occupancy
Included
Cleared for legal occupancy
System development charges & fees
By owner
City fees paid by the owner; we advise on what applies

What an ADU Costs in Portland

ADU cost varies widely with the type and size, the condition of any existing structure, and the site and utility work involved. A garage conversion that reuses a sound foundation is generally the most economical path, an attached or basement ADU sits in the middle, and a detached new build is the largest investment because it adds a foundation, structure, and utility runs. City fees are separate and paid by the owner. Because the range is so wide and site-driven, we price each ADU after a feasibility review rather than quoting a rule-of-thumb number.

What drives the price

  • ADU type: garage conversion, attached or basement, or detached new build
  • Size and level of finish
  • Site conditions, foundation, and utility trenching and connections
  • Structural upgrades needed to make an existing building habitable
  • Kitchen, bathroom, and mechanical selections

You will get a written, itemized estimate before the build is committed, with no verbal numbers and no pressure. To explore what your property can support, request a free estimate or call or text (503) 272-6436.

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What Portland Homeowners Say

VResh Construction has completed more than 500 projects across the Portland metro with a 5.0 rating on Google. The reviews below are pulled live from our Google Business Profile, so what you see is current and unfiltered.

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Serving Portland Metro Area

VResh Construction provides window replacement, siding installation, roofing, dry rot repair and full exterior renovation services throughout the Portland metro area and Southwest Washington.

Portland Metro — Oregon

Portland, OR
Oak Grove, OR
Cedar Mill, OR
King City, OR
Happy Valley, OR
Clackamas, OR
Milwaukie, OR
Gresham, OR
Wood Village, OR
Scappoose, OR
Sandy, OR
Newberg, OR
Estacada, OR
Lake Oswego, OR
Beaverton, OR
Hillsboro, OR
Tigard, OR
Sherwood, OR
West Linn, OR
Oregon City, OR

Southwest Washington

Vancouver, WA
Battle Ground, WA
Woodland, WA
Camas, WA
Ridgefield, WA
Washougal, WA
Kalama, WA

Extended Service Areas

Longview, WA
Kelso, WA
Salem, OR
Seaside, OR
Lincoln City, OR
Long Beach, WA
OUR FAQS

ADU Construction FAQs

What is an ADU?
−
An accessory dwelling unit is a small, self-contained second home on the same property as a main house, with its own kitchen, bathroom, and entrance. It can be detached in the backyard, attached to or inside the existing house including a basement, or a converted garage. Homeowners build them for rental income, family, work space, and added value.
What are the different types of ADUs?
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Three main types. A detached ADU is a standalone backyard structure with the most privacy and the highest cost. An attached or interior ADU is created within or added onto the house, including a basement conversion, and is often more economical. A garage conversion turns an existing garage into living space, reusing a footprint and foundation you already have.
How big can an ADU be in Portland?
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In general, a Portland ADU is capped around 800 square feet or a share of the primary home's size, whichever is smaller, and it must be smaller than the main house, with setback and height limits that affect a detached unit. These rules change over time, so we confirm the current requirements for your specific lot during design.
Do you handle the design and permits?
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Yes. We start with a feasibility and design step, working with our design and architecture partner on the plans, then steer the project through Portland's permit process. Managing the code and permitting is a core part of building an ADU, and we coordinate it as part of the project.
Can I rent out my ADU?
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ADUs are commonly built as long-term rentals, and that income is a major reason homeowners build them. Rules on renting, including any short-term rental permitting and occupancy requirements, are set by the city and change, so we point you to the current requirements as part of planning.
Can my basement or garage become an ADU?
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Often, yes. A basement can be converted into an interior ADU, and a detached garage into a standalone unit, as long as the existing structure is sound and can be brought up to code for habitation, including egress, ceiling height, insulation, and separate systems. We assess the existing building first. For basement groundwork, see our basement finishing page.
How long does it take to build an ADU?
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A conversion can move faster, while a detached new build is a months-long project once design and permitting are added to construction. Permitting timelines in particular vary. We give you a realistic schedule for your ADU type and scope with the estimate.
How much does an ADU cost?
+
It varies widely with the type, size, site, and finish level, plus separate city fees paid by the owner. A garage conversion is usually the most economical, an attached or basement ADU sits in the middle, and a detached new build is the largest investment. We price each ADU after a feasibility review rather than a rule-of-thumb number.
Does an ADU add value to my property?
+
Yes. A permitted, self-contained second unit adds meaningful resale value in Portland and can generate rental income in the meantime, which makes ADUs one of the higher-return projects a homeowner can take on. The exact value depends on the unit and your neighborhood.
Do I have to live on the property?
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Owner-occupancy and related requirements are set by the city and have changed over time, so we confirm the current rules with you during planning rather than relying on what used to be true. It is one of several regulatory items we check for your specific situation.
What utilities does an ADU need?
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An ADU needs water, sewer, and electrical service, and heating, usually a ductless mini-split. A detached unit typically requires trenching and new connections from the main house or street, which is part of why detached builds cost more. We plan the utility work into the design and budget.
Can you match the ADU to my existing home?
+
Yes. Many homeowners want a detached ADU or conversion that echoes the main house's roofline, siding, and trim so the property reads as one cohesive whole, and we design and build to match. Others prefer a clean, modern cottage, which we also build.