Detached ADU (DADU)
Custom backyard cottages designed and built for Whatcom County lots. A completely separate structure with maximum privacy and rental potential.
Attached ADU
Add a self-contained unit to your existing home — basement suites, side additions, or above-garage conversions.
Garage Conversion
Convert your existing garage into a permitted ADU. The lowest-cost entry point for homeowners ready to start building equity.
Basement ADU
Turn your unused basement into a rental-ready dwelling unit. Ideal for homes with existing below-grade space.
Prefab ADU Floor Plans
Fourteen factory-built, CSA A277 certified designs from 200 to 900 sq ft. Delivered by truck, set by crane, finished on site — in Whatcom, Skagit, and Island counties.
Backyard Office & Studio
Insulated, powered, enclosed workspace with no plumbing — often no permit required at all. Around $200/sq ft unpermitted, $300/sq ft permitted on a foundation. No minimum project size.
ADU Design & Architecture
Custom floor plans and architectural design optimized for your lot, zoning, and budget. Our architect works within Whatcom County requirements.
ADU Permitting Services
Site plans, land use permits (county), and building permits — all handled in-house by Loren. Free when we build your ADU.
Sustainable ADU Construction
Energy-efficient, eco-conscious ADU construction. Heat pumps, high-performance envelopes, and all-electric design built above the 2021 WSEC baseline.
Ballpark Pricing
What It Costs Per Square Foot
Three tiers, depending on how far you want to take the structure. Not every project needs to be a full dwelling unit.
Unpermitted Accessory Structure
~$200/sq ft
Insulated, enclosed studio, office, or bonus room. Power only — no plumbing or water, not a dwelling unit.
No building permit required. Typical 100–400 sq ft: $20,000–$80,000.
Permitted Accessory Structure
~$300/sq ft
Permitted and built on a real foundation for use as a bedroom, office, or studio. Still no kitchen or plumbing.
Includes permitting and foundation. Typical 200–500 sq ft: $60,000–$150,000.
Full ADU / DADU
$450–$650/sq ft
Permitted dwelling unit with kitchen, bathroom, and full utility connections. Rentable, financeable, appraisable.
All-in: design, permitting, construction, utilities. Typical 500–1,000 sq ft: $225,000–$500,000.
No Minimum Project Size
A 120 sq ft insulated backyard office is real work to us, same as a 1,000 sq ft DADU. If you only need a quiet room with power and insulation, we will build exactly that and nothing more.
Garage Conversions
Converting a garage into a non-dwelling bonus room is quoted per project after a site visit — the existing structure drives too much of the cost to publish a rate. Garage-to-ADU conversions price at the full dwelling tier.
Three Ways We Build
Prefab, Modular, or Site-Built
Small Prefab Units
We build the unit in the shop, deliver it, then assemble and finish it on site. Fastest path for offices, studios, and bonus rooms.
Full Modular Units
A complete factory-built standalone unit trucked in and set on your site. Fixed price, compressed timeline, site prep runs in parallel.
Full Site-Built
Built entirely on site from the ground up. Adapts to any lot, slope, or custom design — the right call for complex properties.
Modular is the fastest path to a permitted dwelling unit. Browse all 14 prefab floor plans, 200–900 sq ft →
Not Sure Where to Start?
Book a free 30-minute consultation to talk through whether your property qualifies, then review our transparent pricing to understand the full investment. Or see the complete cost breakdown for Whatcom County ADUs.
Why Choose Us for Your ADU Project?
One Team, Start to Finish
You won't get handed off between companies. Loren runs your project end to end — feasibility, permitting, and the build itself — with our architect designing to your lot and Carlos of Monarca Construction building alongside him. One point of contact throughout.
GIS-Powered Feasibility
Our automated GIS pipeline checks your parcel against Whatcom County zoning, critical areas, watershed overlays, and transit routes before you spend a dollar.
2026 Law Experts
HB 1337 changed everything. We stay current on state mandates, Bellingham's December 2025 ordinance updates, and county comprehensive plan amendments.
Transparent Pricing
No surprise change orders. We provide detailed cost breakdowns by phase so you know exactly what you're paying for at every stage.
