ADU Builder in Bellingham, WA

Accessory dwelling units (ADUs) are one of the smartest ways to add living space, rental income, or room for family to a Bellingham property. Monarca Construction & Remodeling designs and builds ADUs across Bellingham and Whatcom County — from detached backyard cottages to garage and basement conversions — handling everything from design and permitting through the finished, move-in-ready build.

What is an ADU?

An accessory dwelling unit is a self-contained second home on the same lot as your primary house, with its own kitchen, bathroom, and entrance. In Whatcom County, ADUs generally take one of three forms:

• Detached ADU — a standalone cottage in the backyard, ideal for privacy and rental potential.
• Attached ADU — an addition connected to your existing home with a separate entrance.
• Conversion ADU — a garage, basement, or unused portion of the home converted into a full living unit.

Why build an ADU in Bellingham?

Washington has expanded where and how homeowners can add ADUs, making them easier to permit than ever — and in a tight housing market like Bellingham’s, that opens real opportunity:

• Rental income — a long-term or mid-term rental unit that can help offset your mortgage.
• Multigenerational living — a comfortable, independent space for aging parents or adult children.
• Flexibility & value — a home office, guest suite, or studio today that adds lasting resale value tomorrow.
• Aging in place — a single-level, accessible unit that lets family stay close.

Our ADU process

We manage the entire project as one accountable team, so you’re not juggling separate designers, permit expeditors, and subcontractors:

1. Consultation — we visit your property, review your goals, and assess what your lot and budget will support.
2. Design & planning — we develop a layout that fits your site, your style, and local requirements.
3. Permitting — we prepare and submit plans and coordinate with the City of Bellingham or Whatcom County so the project is approved and built to code.
4. Construction — our crew self-performs the build, keeping the site clean and you informed at every stage.
5. Final walkthrough — we walk the finished unit together and stand behind our work.

Built for the Pacific Northwest

Every Monarca ADU is built for how we live here — proper insulation and ventilation for our damp climate, durable exterior materials, and finishes that match the character of your main home. As a licensed, bonded, and insured Washington contractor, we build ADUs that are comfortable, efficient, and made to last.

Thinking about an ADU on your Bellingham property? Request a free estimate or call (360) 392-5577 — we’ll help you understand what’s possible on your lot.