Full-Service ADU Builder Serving Bellingham & Whatcom County
Bellingham ADU Builders operates as a dedicated ADU contractor serving Bellingham, Ferndale, Lynden, and unincorporated areas throughout Whatcom County. They offer a complete, done-for-you service — from initial feasibility study through final keys — with a licensed architect on staff, a dedicated permitting specialist, and GIS-powered lot analysis built into their process.
Their team is structured to keep clients with a single point of contact throughout the entire project. Carlos coordinates architectural drawings, structural engineering, and build execution, while Loren manages every permit submission and follows up directly with county staff to keep projects moving through the approval pipeline without delays.
To help homeowners get started, they offer a free feasibility study that analyzes a property using Whatcom County GIS data and current 2025 land use rules, delivered within 48 hours. The report checks parcels against zoning, critical areas, watershed overlays, and transit routes before any money is spent.
Detached ADU and Attached ADU Construction
As an experienced detached ADU builder and accessory dwelling unit builder, Bellingham ADU Builders handles both detached and attached ADU projects across Whatcom County. A Detached Accessory Dwelling Unit (DADU) is a self-contained structure built separately on the property — ideal for maximizing rental income, creating multigenerational living arrangements, or building long-term property value. Detached ADU construction in Whatcom County typically ranges from $250,000 to $550,000+, depending on size, finishes, site complexity, and utility connections.
Their detached ADU service includes:
- Custom architectural design optimized for lot constraints and setbacks
- Full permitting through Bellingham or Whatcom County
- Foundation, framing, plumbing, electrical, and finish work
- Kitchen, bathroom, and laundry hookups
- Energy-efficient construction qualifying for the 30% federal tax credit
- Separate utility connections where required
- Final inspection coordination and certificate of occupancy
As an in-law suite builder and attached ADU specialist, they also construct units within or physically connected to an existing home — including basement conversions, side additions, and above-garage units. Attached ADUs typically range from $200,000 to $400,000+ and are often the most cost-effective option due to shared structural elements and utility connections. Under Bellingham's updated code (BMC 20.10.036), basement conversions are exempt from the 1,000 sq ft size limit if the primary dwelling has been on the property for five or more years.
Under Washington's HB 1337 and Bellingham's December 2025 ordinance update, most residential lots can now support up to two ADUs — meaning a backyard cottage alongside a basement conversion is fully permitted. Key statewide changes include:
- Right to Build: All Washington cities and counties must allow ADUs by right
- No Owner Occupancy: Owner-occupancy requirements have been eliminated statewide
- Reduced Setbacks: Setbacks reduced to 5 feet in many cases
- Impact Fee Limitations: Restrictions on impact fees for ADUs under 1,000 sq ft
Permits Included With Every Build
Bellingham ADU Builders absorbs the entire permit package — site plans, land use permits, building permits, and engineering — into the construction contract at no additional charge. ADU permitting in Whatcom County involves navigating state mandates, city-specific ordinances, county regulations, and environmental overlays, and their team is built to handle all of it.
Their permit package covers professional site plans, land use permits (required for unincorporated county properties), and building permits with tiered pricing based on project complexity. The total typically runs less than 1% of the project cost, plus $1,000–$2,000 in government filing fees. For those who need permits without a full build contract, a standalone permit service is also available.
Properties within the Lake Whatcom Watershed are currently prohibited from ADU construction under Chapter 16.80 BMC. Their automated feasibility study checks watershed status automatically, ensuring homeowners know their options before committing to any project.