Seattle DADU & ADU Builder
Transform your Seattle property with a professionally built accessory dwelling unit. Whether you're adding rental income, creating space for family, or maximizing your lot's potential — we handle permits, design, and construction from start to finish.
Seattle DADU Experts Since 2012
Seattle's ADU boom isn't slowing down — and for good reason. With housing costs climbing and lot sizes staying fixed, homeowners are looking up, down, and back to find more space. A detached accessory dwelling unit (DADU) or attached ADU can generate $2,000-3,500+ in monthly rental income, provide housing for aging parents, or give adult children a landing pad without sacrificing your privacy.Waltier Homes has been building in Seattle for over 12 years. We've watched ADU regulations evolve, navigated the permitting process through multiple policy changes, and completed DADU projects across neighborhoods from Ballard to Beacon Hill. That experience means fewer surprises, faster permits, and builds that meet code the first time.Seattle's ADU rules are some of the most permissive in the country — but they're also complex. Lot coverage limits, setback requirements, design review districts, tree protection ordinances, and utility capacity all affect what you can build and where. We evaluate all of this before you commit to anything.
Attached ADUs (AADUs) Units built within or attached to your existing home. Basement conversions, garage apartments, attic buildouts, and bump-out additions all qualify. Often more cost-effective than detached units, with easier utility connections and sometimes simpler permitting.
Basement ADUs Seattle's hilly terrain means many homes have daylight basements with ADU potential. We handle egress requirements, separate entrances, soundproofing, plumbing, electrical upgrades, and all permit requirements. A well-designed basement ADU can feel like a standalone apartment.
Garage Conversions Convert an existing detached garage into living space, or build a new structure with living quarters above parking. These hybrid structures maximize lot utility while maintaining vehicle storage.
Seattle ADU Rules & Requirements
Seattle has progressively loosened ADU restrictions over the past decade. Here's the current landscape:
Size Limits: DADUs: Up to 1,000 square feet (or 1,200 SF with affordable housing commitment)AADUs: Up to 1,000 square feetCombined: You can have both a DADU and an AADU on one lot in most zones
Lot Requirements: Minimum lot size requirements have been eliminated in most residential zonesLot coverage limits still apply (typically 35-50% depending on zone)Maximum hardscape limits affect total impervious surface
Setbacks: Rear setback: Typically 5 feet (reduced from previous requirements)Side setback: 5 feet in most casesHeight limits: 12 feet within rear setback, up to 22 feet elsewhereParking:No off-street parking required for ADUs in most of SeattleExisting parking cannot be eliminated in some zones
Owner Occupancy: Seattle has suspended owner-occupancy requirements through at least 2027You do NOT need to live on the property to build or rent an ADU
Design Review: Projects in designated design review districts require additional approvalWe navigate this process regularly in neighborhoods like Ballard, Fremont, and Capitol Hill
Short-Term Rentals: ADUs can be used for short-term rentals if you obtain a short-term rental operator licenseLong-term rental restrictions are minimal
Ready to build something real
Let's talk about your project and what it means to you
