How Much Does It Really Cost to Build an ADU in Central Oregon (2025 Edition)

If you’re considering adding an accessory dwelling unit (ADU) on your property in Central Oregon, one of the first questions you’ll ask is: “How much is this going to cost? ”The truth: there’s no fixed number. Costs vary widely depending on the type of ADU, lot conditions, finish level, and location (city vs rural). But in 2025, with updated rules and strong demand in the Bend & Deschutes County region, you can better estimate and plan your project.

In this post, we’ll break down cost ranges, what drives those costs, how Central Oregon is distinctive, and how you can budget smartly.

Typical Cost Ranges for ADUs in Oregon & What That Suggests for Central Oregon

Here are some general cost data points for ADUs in Oregon and across the U.S.:

• According to Angi, ADU construction averages about $150-$300 per square foot nationally in 2025, with some units going higher than $600/ft². Angi

• A recent Oregon-specific guide shows: conversions (garage/basement) might run $50,000–$100,000, small detached units (400-600 ft²) often $100,000–$180,000+, and larger detached ADUs (600-800+ ft²) trending toward $180,000–$250,000+. autonomous+2Central Oregon ADU+2

• For Bend specifically: one local source estimates building an 800-square-foot ADU at $225,000–$350,000+ in the Bend market. REALTOR® in Bend

What this means for Central Oregon in 2025:

• If you’re converting existing space (garage, basement) in or near Bend, expect $100K–$180K as a rough ballpark.

• For a new detached ADU of 600-800 ft² with standard finish, you’d likely budget $200K–$300K+, especially if utilities or site work are complex.

• Keep in mind: lot condition (slope, trees, access), utility hookups (septic vs city sewer), design/finish quality, and permit fees all make a big difference.

What Drives the Cost? Key Cost Drivers You Should Know

When you break down the cost, several factors push the number up or down:

• Size & Layout: Larger ADUs cost more, but per-square-foot costs may drop slightly with scale.

• Type of Unit: A detached new build with its own foundation, utilities, and structure will cost significantly more than a conversion of an existing space.

• Finish level & quality: Standard finishes cost less; high-end finishes, specialty architecture, or unique materials add cost.

• Site conditions & access: If your lot is steep, in a wildfire risk zone, has difficult access, or needs significant grading/tree removal — costs increase.

• Utility hookups & infrastructure: If you need to add sewer/septic, water lines, new meter, electrical upgrades (200-amp panel for two units?), that adds thousands. Better Homes & Gardens+1

• Permitting, fees, and soft costs: Design/architect fees, engineering, permits, SDCs (system development charges) — these often add 10-25% on top of hard construction costs. Tegman Custom Homes LLC+1

• Local labor and materials market: Central Oregon’s building market has premium pricing due to demand, which may drive higher costs than some national averages.

• Zoning and regulatory compliance: Rural lots in Deschutes County have additional requirements (wildfire defensible space, septic design, access) that can increase cost.

Cost Breakdown: Sample Budget for Central Oregon ADU (2025)

Here’s a projected budget for a 700 ft² detached ADU in Bend, moderate finishes, standard site (city utilities available). Use this as a framework, adjust for your lot and design.

Expense Category	Estimated Range
Design & Engineering	$8,000 – $20,000
Site Work (grading, utilities)	$15,000 – $40,000
Foundation & Structure	$35,000 – $60,000
Exterior (roofing/siding/windows)	$30,000 – $50,000
Interior Finishes & Systems	$70,000 – $120,000
Utility Connections & Hookups	$10,000 – $30,000
Permits, Fees & SDCs	$10,000 – $30,000
Contingency (10%)	$15,000 – $30,000
Total Estimated Budget	$193,000 – $380,000

Based on this table, you can reasonably expect the cost to float around $200K to $300K for a well-designed unit in the Bend area — assuming no major surprises.

If your lot is rural in Deschutes County, or you’re adding complex site work or wildfire mitigation, expect the budget to skew toward the higher end.

Strategies to Control Your Cost

Here are some tactics local homeowners in Central Oregon use to keep their ADU build on budget:

• Choose an attached or conversion unit (garage/basement) when possible — less site work, less infrastructure.

• Use pre-approved ADU plans — some cities offer standard plans that reduce design/engineering time and cost. Bend offers this. Reddit+1

• Stay within the 800 ft² ADU cap — in Bend, an ADU over ~800 ft² may trigger higher fees or become classified differently. REALTOR® in Bend

• Select moderate finishes — avoid premium materials for lower ROI unless your budget allows.

• Maximize existing utilities — if your lot already has the capacity for extra unit, you save on hookup costs.

• Budget for contingency — unexpected site issues (e.g., rock excavation, tree removal, soil issues) can add big cost.

• Vet your contractor carefully — pick builders familiar with local codes, ADU permitting, and Central Oregon conditions.

Why Central Oregon Is a Unique Case

• High housing demand: With Bend and Redmond’s housing markets tight, rental demand for ADUs is strong — which makes the investment more justifiable.

• Lot and utility variations: Many properties near Bend have city sewer/water; rural lots in Deschutes County may rely on septic and wells, which changes cost dynamics.

• Wildfire & terrain risks: Rural lots or lots on the outskirts may require additional fire-mitigation measures or site prep, raising cost.

• Permitting changes: In 2025 the regulations are more ADU-friendly in Bend, which can reduce delays and fees — but good design and permitting still matter.

• Resale value potential: In Central Oregon, a permitted ADU can noticeably raise property value — adding more upside to the cost investment.

Building an ADU in Central Oregon is a substantial investment — but one with compelling upside in 2025 given the region’s housing dynamics, updated regulations, and strong rental demand.If you approach the budgeting process with realistic expectations, plan for key cost drivers, and work with professionals familiar with Bend and Deschutes County, you’ll be in a strong position to build smart and build well.

Thinking about your own ADU project? Reach out to a local expert — build-ready plans, cost estimates, and permit guidance can help you decide whether the investment aligns with your property and goals.

FAQs: Central Oregon ADU Cost (2025)

Q: What’s the minimum budget I should plan for an ADU in Bend?

A: For a basic conversion or small attached unit — maybe $120K–$180K — but true realistic budgets are often $200K+ once you include soft costs and site work.

Q: Does building an ADU always make financial sense?

A: Not always. It depends on rental income potential, zoning/rental restrictions, lot suitability, and overall budget. But in Central Oregon’s market, many homeowners find the return worthwhile.

Q: How much do later finishes and upgrades impact cost?

A: Finishes can add tens of thousands of dollars. For example, standard finishes may keep cost to around $200/ft²; premium finishes or complex architecture can push $300-$400+/ft².

Q: Will my property taxes go up after building an ADU?

A: Yes. Adding an ADU increases your property’s assessed value, which will raise taxes — but many owners offset that via rental income.

Q: Are there cost differences between city and county lots?

A: Yes. Rural county lots often incur higher costs for site work, septic or well systems, fire mitigation, and longer build timelines — meaning higher budgets than city lots.