Converting Existing Spaces: Turning Garages & Basements into ADUs in Central Oregon (2025 Guide)

Accessory Dwelling Units (ADUs) are booming across Central Oregon, and not just the detached backyard cottages you see in new builds. One of the smartest (and often most affordable) ways to create an ADU in 2025 is by converting an existing garage or basement.

These conversions make use of spaces you already have—avoiding the high costs of new foundations, additional framing, and major site work. Whether you're looking to house family, generate rental income, or boost your property’s value, garage and basement conversions offer a fast and efficient path to adding livable space.

Below is everything you need to know before getting started.

Why Conversions Are So Popular in 2025

Homeowners throughout Bend, Redmond, Sisters, and Deschutes County are increasingly choosing conversions because:

✓ Lower Cost

You’re working with a structure that already exists—meaning major components like the roof, framing, and foundation are there.

✓ Faster Timelines

Conversions usually take 3–6 months, compared to 8–12+ months for new detached ADUs.

✓ More Flexible Designs

Basements and garages offer blank-slate interiors ideal for studios, 1-bedroom, or even 2-bedroom layouts.

✓ Minimal Impact to the Property

No need to carve out backyard space or navigate complex lot coverage calculations.

Garage Conversion ADUs

What’s Involved?

Most garage conversions require upgrades such as:

• Insulation & moisture protection

• Raising the floor to meet code

• Adding plumbing lines (bathroom + kitchenette)

• Electrical upgrades

• Heating, cooling, and ventilation

• New windows & exterior access

Cost Range in Central Oregon

$90,000 – $175,000 depending on size, plumbing distance, and level of finish.

Detached garages usually cost more than attached ones, since utilities may be farther away.

Zoning Considerations

In Bend and Deschutes County:

• You must convert the space fully into habitable living area—no partial garage/partial storage.

• Parking replacement is no longer required in most Bend zones (huge benefit).

• Setbacks don’t change since the structure already exists.

Best Uses

• Long-term rental

• Housing for a parent or adult child

• A small studio apartment for travel nurses or seasonal workers

Basement Conversion ADUs

Basements aren’t as common in Central Oregon as garages, but when they exist, they can make an ideal ADU.

What’s Involved?

To meet code, basement ADUs typically need:

• Proper ceiling height (usually 7 ft minimum)

• A legal egress window or exterior exit

• Moisture sealing & insulation

• Upgraded mechanical ventilation

• Independent heating zones

Cost Range

$65,000 – $150,000, depending on:

• Excavation or structural changes

• Egress window installation

• Plumbing complexity

If the basement already has decent height and access, it can be one of the most affordable ADU types.

Zoning Considerations

Basement ADUs are often easier to approve because:

• Setbacks don’t apply

• Exterior aesthetics remain unchanged

• They don't add height or mass to the property

But you still need full ADU permitting.

Best Uses

• Long-term rental

• Full-time family housing

• “Lock-off suite” for blended families

• Stable income with lower tenant turnover

Pros & Cons of Converting Existing Spaces

Pros

• Lower cost than building new

• Faster permitting and construction

• Strong rental potential

• Minimal change to property layout

• Adds value without major expansion

Cons

• Garage space is permanently lost

• Basements may feel darker without good design

• Plumbing may require creative routing

• Some layouts can feel limited

Design Tips for Exceptional Conversions

1. Maximize Natural Light

Add:

• Large egress windows

• Skylights (for garages)

• Glass entry doorsThis makes tight spaces feel larger.

2. Maintain Separation from the Main House

Include:

• A dedicated entrance

• Acoustic insulation

• Clear privacy boundaries

3. Choose Space-Saving Fixtures

Think:

• Compact kitchens

• Stackable washer/dryer units

• Pocket or barn doors

4. Add Heating & Cooling Independence

Mini-split systems are ideal—efficient and affordable.

5. Plan Storage Carefully

Reuse under-stair space or add built-ins to maximize functionality.

Is a Garage or Basement Conversion Right for Your Property?

A conversion ADU is perfect if:

• Your lot can’t accommodate a detached ADU

• You want the most affordable ADU option

• You don’t want major construction in the yard

• You’re aiming for long-term stability and ROI

With Central Oregon’s continued housing demand, conversions remain one of the best ways to add value quickly without the cost of building from scratch.

Thinking About Converting Your Garage or Basement?

I can break down:

• What your property is allowed to do

• Estimated costs based on local 2025 rates

• Whether a garage or basement ADU fits your long-term goals

• Permit requirements for Bend vs. Deschutes County

Just let me know your address and your plans—I’ll help you figure out the best path.

FAQs

1. Is it cheaper to convert a garage or basement compared to building a detached ADU?

Yes. Conversions are typically 30–50% cheaper because the foundation, walls, and roof already exist. A garage or basement conversion in Central Oregon typically ranges from $65,000–$175,000, while detached ADUs often exceed $200,000.

2. Do I need a permit to convert my garage or basement into an ADU in Bend or Deschutes County?

Absolutely. All ADUs—converted or newly built—require permits for:

• Building

• Mechanical

• Electrical

• PlumbingAnd in some cases, zoning review.The good news is that Bend has streamlined the ADU permit process significantly in recent years.

3. Will I lose my parking if I convert a garage into an ADU?

In most Bend zones, replacement parking is no longer required, which makes garage conversions much easier. Deschutes County rules vary slightly, depending on the property and zoning.

4. Does a basement ADU need an exterior entrance?

Not necessarily. An interior entrance is allowed, but you must have a legal egress path, such as:

• An egress window

• A door to the exteriorMany homeowners add a separate entrance for privacy and rental flexibility.

5. What ceiling height is required for a basement ADU?

Most spaces must meet a 7-foot minimum ceiling height (after finishes). If your basement is lower, you may need to consider excavation—or choose another ADU option.

6. Can I still use part of the garage for storage?

Only if the ADU is 100% separate and code-compliant. Garage ADUs generally need the full space converted into habitable area. You can add new exterior storage (like a shed) if needed.

7. How long does a conversion typically take?

• Design & permitting: 1–3 months

• Construction: 3–6 monthsDetached ADUs often take much longer because they require more site work and utility extensions.

8. Will converting my basement or garage increase my property value?

Yes—ADUs in Bend and Deschutes County generally add 15–25% to home value, depending on size, quality, and rental potential. A permitted conversion is significantly more valuable than an unpermitted space.

9. Can I use my converted ADU as a short-term rental?

This depends on your location:

• Bend: STR rules are stricter and often capped by zone.

• Deschutes County: More flexible, but varies by area.

• Redmond, Sisters: Additional rules apply.Long-term rental use is always allowed with a permitted ADU.

10. Do I need to upgrade utilities for an ADU conversion?

Possibly. Common upgrades include:

• Electrical panel expansion

• Sewer line upgrades

• New plumbing routes

• Dedicated heating/cooling (often a mini-split)

Your contractor or designer can assess your current system.

11. Can I convert only half of my garage or basement into an ADU?

Usually no. ADUs must be fully self-contained units with:

• Sleeping area

• Bathroom

• Cooking facilitiesSome areas allow “junior ADUs,” but these are not widely adopted in Oregon yet.

12. Are detached garages easier or harder to convert?

Detached garages can be more expensive because utilities may need to be trenched out to the structure. But zoning rules often treat conversions more favorably than new detached ADUs.

13. Can I DIY my garage or basement conversion?

You can do some portions yourself, but Oregon requires licensed pros for:

• Electrical

• Plumbing

• MechanicalFull DIY attempts often fail inspections, take longer, and cost more to fix than doing it right the first time.

14. Do conversions have to meet new-building energy codes?

Yes. Even though the structure is existing, the interior must meet current energy standards, including insulation, windows, and ventilation requirements.