Garage ADU Portland: What You Can Build Above or Inside Your Garage

A garage ADU in Portland is one of the most efficient ways to add a dwelling unit
without consuming additional yard space. Garage ADUs may be created by converting an existing garage,
building above an existing structure, or constructing a new garage with an ADU above.

What Is a Garage ADU?

A garage ADU is an accessory dwelling unit that is located within or above a garage structure.
In Portland, garage ADUs are commonly built as second-story units above detached garages
or through the conversion of existing garages into habitable space.

Because garages were not originally designed for living space,
garage ADUs require careful evaluation of zoning, structural capacity,
and building code requirements before design begins.

Garage ADU Zoning Rules in Portland

Garage ADUs are allowed in many Portland residential zones,
but approval depends on height limits, setbacks, floor area allowances,
and the location of the existing garage on the lot.

Above-garage ADUs must comply with maximum building height
and may be affected by rear-yard setback requirements.
Converted garages must also meet minimum ceiling heights,
egress, and fire separation standards.

Structural and Code Considerations

Most existing garages were not engineered to support a second-story dwelling.
Structural upgrades are often required, including new foundations,
shear walls, and seismic reinforcement.

Fire separation, sound control, and energy code compliance
are also key considerations when converting or building a garage ADU.

Why Feasibility Comes Before Design

Garage ADU projects frequently face delays when structural or zoning constraints
are discovered after drawings are prepared.
Confirming garage ADU feasibility in Portland early
helps avoid redesigns, added costs, and permit corrections.

A feasibility review verifies whether your garage ADU concept
is realistically approvable before investing in full construction plans.

How the ADU Feasibility Wizard Helps

Our interactive

ADU Feasibility Wizard

evaluates garage ADU potential across Portland and the surrounding PDX region,
including Beaverton, Gresham, Hillsboro, Salem, Keizer, and Marion County.

For a $250 upgrade, the Wizard allows you to download preliminary ADU plans
or upload your own drawings to confirm zoning compliance,
height limits, setbacks, and structural feasibility.

Start With Feasibility Before You Build

If you’re considering a garage ADU in Portland,
start with feasibility before committing to design.
Use the

ADU Feasibility Wizard

to evaluate your lot and move forward with confidence.