Professional Home Addition Services
Expand Your Living Space
With KOI Build Co
Custom home additions, sunrooms, master suites, and bonus rooms. Professional design-build services across South Puget Sound.
Why Choose Us
Olympia's Trusted Addition Experts
With over 20 years of experience, KOI Build Co has become the go-to home addition contractor for homeowners across South Puget Sound. We specialize in expanding your living space with quality craftsmanship.
Our Work
Featured Projects
Real results from homeowners who trusted us.
Olympia, WA
Second Story Addition
Added a full second story with 3 bedrooms and 2 bathrooms.
Olympia, WA
Second Story Addition
Added a full second story with 3 bedrooms and 2 bathrooms.
Lacey, WA
Master Suite Addition
Luxurious master bedroom with spa-inspired bathroom.
Lacey, WA
Master Suite Addition
Luxurious master bedroom with spa-inspired bathroom.
Tumwater, WA
Sunroom Addition
Beautiful four-season sunroom with panoramic windows.
Tumwater, WA
Sunroom Addition
Beautiful four-season sunroom with panoramic windows.
Olympia, WA
Family Room Extension
Spacious family room addition with vaulted ceilings.
Olympia, WA
Family Room Extension
Spacious family room addition with vaulted ceilings.
Lacey, WA
Garage Conversion
Converted attached garage into functional living space.
Lacey, WA
Garage Conversion
Converted attached garage into functional living space.
Olympia, WA
In-Law Suite
Private in-law suite with separate entrance.
Olympia, WA
In-Law Suite
Private in-law suite with separate entrance.
Olympia, WA
Home Office Addition
Custom home office with built-in bookshelves.
Olympia, WA
Home Office Addition
Custom home office with built-in bookshelves.
Lacey, WA
Mudroom Addition
Functional mudroom with custom storage.
Lacey, WA
Mudroom Addition
Functional mudroom with custom storage.
"KOI added a master suite to our home. The results are stunning!"
Robert & Susan M.
Olympia, WA • Master Suite Addition
How We Can Help
Comprehensive Solutions
From emergency repairs to complete replacements, we provide full-service solutions tailored to your needs.
Free Design Consultation
We'll discuss your vision and provide expert recommendations.
Permit Management
We handle all permits, zoning, and building code compliance.
Licensed & Insured
Fully licensed general contractors with comprehensive insurance.
On-Time Delivery
Most additions completed within 8-12 weeks with regular updates.
Get In Touch
Let Our Experts Answer Your Questions
Schedule your free consultation today. Our team is ready to help.
Ready to Expand Your Home?
Let's Bring Your Vision to Life
Contact us today for a free, no-obligation consultation.
Free estimate • No obligation • Licensed & insured