Accessory Dwelling Units (ADUs) have quickly become one of the most practical and profitable remodeling trends in Seattle. Whether you’re looking to create rental income, support multi-generational living, or boost your property’s value, an ADU can be a game-changing addition to your home.

In this guide, we’ll explore what ADUs are, why they’re in high demand in Seattle, and how Blue Water Design Build helps homeowners create beautiful, functional secondary dwellings.

What Is an ADU?

An Accessory Dwelling Unit is a smaller, self-contained living space on the same lot as a single-family home. Seattle recognizes several types of ADUs:

• Attached ADU (AADU): A converted part of your existing home, such as a basement or attic.
• Detached ADU (DADU): A free-standing unit, often built in a backyard or above a garage.
• Garage Conversions: Existing garage structures transformed into legal living spaces.

Each type includes a kitchen, bathroom, living area, and sleeping space, ideal for independent occupancy.

Why Are ADUs So Popular in Seattle?

Legal & Encouraged

Seattle’s zoning rules have evolved to encourage ADUs, easing size, height, and occupancy restrictions. In most neighborhoods, you can now build both an AADU and a DADU on the same property.

Rental Income Potential

Long-term or short-term (30+ day) rental income can offset mortgage payments or fund other renovations. Some homeowners generate $1,500–$2,500/month depending on location and finishes.

Flexible Living Options

Perfect for aging parents, returning college students, guests, or live-in caregivers—an ADU offers independence with proximity.

Boost Property Value

A professionally built ADU can increase home resale value significantly in today’s market.

What Does It Take to Build One?

1. Feasibility Study

We’ll assess your lot, zoning designation, and existing structures to determine the best path forward.

2. Design & Permitting

Blue Water Design Build handles layout, aesthetics, and code compliance, ensuring it fits your property and lifestyle while streamlining approvals with the City of Seattle.

3. Construction

We build to the same standards as any full residence; durable, energy-efficient, and built to last.

Seattle ADU Code Highlights (as of 2025)

• Max DADU size: 1,000 sq. ft. (larger on bigger lots)
• Parking: No off-street parking required
• Owner occupancy: No longer required for most properties
• Separate utilities: Optional but useful for rental tracking

Always consult Seattle DCI or work with an experienced team to understand the latest regulations.

Why Work with Blue Water Design Build?

We’ve designed and built ADUs across Seattle, from basement conversions in Ballard to backyard DADUs in Magnolia. Our process balances architecture, permitting, and construction to help you maximize space, value, and livability.

Considering an ADU? Let’s explore your property’s potential together.