It’s a Good Time to Build an ADU in Spokane
Spokane’s housing landscape is changing, and accessory dwelling units (ADUs) are leading the charge. Whether you call them mother-in-law suites, granny flats, or backyard cottages, these compact living spaces are becoming an increasingly popular solution for Spokane homeowners.
Recent changes to city regulations have made ADUs more accessible than ever, and the numbers tell the story: permit applications have doubled since the city loosened restrictions in 2022.
If you’re a Spokane homeowner wondering whether an ADU makes sense for your property, you’re asking the right question at the right time.
In this guide, we’ll break down the benefits, costs, regulations, and practical considerations to help you decide if an ADU is right for you. And if you’re ready to explore custom ADU plans in Spokane, we can help with that too.
A well-designed detached ADU offers independent living space while enhancing the overall aesthetic and value of your Spokane property.
Here is an ADU in Spokane Valley we recently designed and built.
What is an ADU?
An accessory dwelling unit is a separate, self-contained living space on the same property as a single-family home.
Think of it as a complete mini-home with its own kitchen, bathroom, sleeping area, and entrance.
ADUs come in two main types:
Attached ADUs
Built into or onto your existing home (basement apartments, garage conversions, or additions).
Detached ADUs
Standalone structures in your backyard (new cottages or converted outbuildings).
Both serve the same purpose: independent living space for family, rental income, or flexible use.
Spokane’s housing context: why building an ADU makes sense now
Spokane faces a housing shortage and affordability challenges. Demand for smaller, more affordable units is rising.
The city responded in 2022 by loosening ADU restrictions:
Larger allowable sizes
No design matching requirements
No owner-occupancy requirement
Permit numbers increased significantly after these changes.
Looking ahead, Spokane plans even more flexible rules, including allowing up to two ADUs per property and increasing size limits to 1,000 sq ft.
Financial benefits of building an ADU in Spokane
Property value increase
A well-built ADU can increase property value by 30%–35%.
Rental income
ADUs can generate steady monthly rental income due to strong demand for small housing units.
Construction cost ranges
Type Size Cost
Compact detached 300–700 sq ft $115,000–$175,000
Garage apartment ~600 sq ft $200,000–$250,000
High-end custom varies $450,000–$600,000
Family and lifestyle benefits
ADUs are not just financial investments—they solve real-life needs.
Multi-generational living
Perfect for aging parents or adult children needing independence but staying close.
Flexibility
Rental income
Home office or studio
Guest space
Downsizing option later in life
ADU regulations in Spokane
Size limits
Attached: up to 800 sq ft
Detached: up to 975 sq ft (soon 1,000 sq ft)
Lot requirements
Minimum lot size: 5,000 sq ft (city)
Setbacks: typically 5 ft rear/side
Parking
No extra parking required in most cases
Transit proximity can waive requirements entirely
Permitting process
Apply to City of Spokane
Receive approval letter
Record with County Auditor
Submit confirmation
Obtain building permit
Design considerations for Spokane climate
Strong insulation for cold winters
Efficient HVAC systems
Smart storage solutions
Maximized natural light
Getting started
Start with the City of Spokane Middle Housing Support Team:
MiddleHousing@spokanecity.org
(509) 625-6500
Then:
Define your goals (rental, family, flexibility)
Choose a designer/contractor
Plan for 6–12 months total timeline
Is an ADU right for your property?
Ask yourself:
Do you need family housing flexibility?
Would rental income help?
Is your lot large enough?
Do you want long-term property value growth?
If yes, an ADU may be a strong option.
Frequently Asked Questions
How much does an ADU cost in Spokane?
Between $115,000 and $600,000 depending on size and finish.
What size ADU can I build?
Up to 800 sq ft (soon 1,000 sq ft).
Do I need to live on-site?
No, owner-occupancy is not required.
Can I use rental income for mortgage qualification?
Yes, through Fannie Mae guidelines with appraisal.
How long does construction take?
About 4 months of building time, 6–12 months total including planning.
Final note
ADUs in Spokane are becoming one of the most practical ways to increase housing flexibility, generate income, and add long-term property value.
