How Much Does It Cost to Build an ADU in Spokane or North Idaho?
Accessory Dwelling Units (ADUs) are on the rise in Spokane, Coeur d'Alene, and surrounding communities—from backyard cottages in South Hill to garage conversions in Sandpoint. Whether you’re building space for family, planning for rental income, or preparing for multi-generational living, ADUs can be a smart investment.
But how much does it actually cost to build one?
Let’s walk through the real numbers and factors that impact ADU pricing in the Inland Northwest.
What Counts as an ADU?
An ADU (Accessory Dwelling Unit) is a secondary residential structure on the same property as a primary home. It might be:
- A detached unit in your backyard
- A garage conversion with a separate entrance
- A basement apartment with a kitchenette and bath
Every type has unique permitting, utility, and design considerations—which affects cost.
Local ADU Costs: Why the Range is Wide
In Spokane and North Idaho, ADU construction costs typically range from $180,000 to $350,000+ depending on type, finishes, size, and site conditions. Here’s why the range is so broad:
1. Site Prep & Utilities
A flat city lot with nearby sewer and water access will cost far less than a sloped rural parcel needing septic, grading, or trenching.
2. Foundation Type
Building on a new slab vs. converting an existing garage or basement has a significant impact on labor and material needs.
3. Design Complexity & Finish Level
A simple 600 sq ft one-bedroom ADU with standard finishes will cost far less than an 800+ sq ft unit with vaulted ceilings, custom cabinetry, and high-end appliances.
4. Permitting & Zoning Requirements
Each jurisdiction (Spokane, Post Falls, Hayden, etc.) has its own ADU rules. Some require owner-occupancy affidavits, parking stipulations, or architectural reviews—which can affect both timeline and budget.
Example Cost Comparison: Flooring & Counters
To highlight just how material choices affect the budget:
Flooring: Laminate plank may cost $3–$6/sf installed, while engineered hardwood runs $8–$14/sf.
Counters: Laminate tops might cost $1,500, while mid-tier quartz could push that to $3,500+ for the same footprint.
Multiply those changes across a kitchen, bath, and living space, and small choices can quickly swing a budget by tens of thousands.
How The Building Company Helps Navigate It All
ADUs can feel overwhelming. You’re managing:
- Utility tie-ins
- Budgeting unknowns
- Zoning and permitting nuances
We’ve helped homeowners across Spokane County and Kootenai County bring ADUs to life—by starting with the right plan. While we work with local design partners for architectural and engineering drawings, our job is to:
- Help you identify feasibility
- Coordinate with city/county planning
- Provide detailed scope and budget breakdowns
- Guide you through every phase of the build
We take the guesswork out—and help you make smart, informed decisions.
Considering an ADU? Let’s Talk.
Whether you’re in Mead, Liberty Lake, Coeur d’Alene, or Rathdrum, building an ADU is doable—you just need the right partner.
📱 Call or text: 509-625-6500
📧 Email: info@pnwbuild.com
🔗 Reach out today: www.pnwbuild.com/contact
The Building Company
is a proud member of the National Association of Home Builders (NAHB) and the National Association of the Remodeling Industry (NARI). These affiliations reflect our commitment to professionalism, continuing education, and high industry standards.
