Date Created: 4/1/2026
If you own a home in Edmonds, Lynnwood, Mountlake Terrace, or anywhere in Snohomish or King County, Washington State has handed you a significant opportunity. A sweeping change to state law now makes it easier than ever to build an Accessory Dwelling Unit (ADU) or Detached Accessory Dwelling Unit (DADU) on your property and homeowners across the region are taking notice.
At Plumb Perfect Builders, we've had a sharp uptick in homeowners asking about ADU and DADU construction. Here's everything you need to know about the new rules and why now might be the perfect time to build.
An Accessory Dwelling Unit (ADU) is a secondary living space attached to or within your primary home think a finished basement apartment, an in-law suite, or a converted garage. A Detached Accessory Dwelling Unit (DADU) is a fully separate, standalone structure on your property, like a backyard cottage or carriage house.
Both can be rented out for income, used for family members, or serve as a long-term investment that adds real equity to your property.
Washington passed legislation (HB 1337) that dramatically expanded homeowner rights around ADUs. Here are the key changes every Snohomish and King County homeowner should know:
Up to 2 ADUs per lot. Homeowners can now build up to two ADUs on a single-family residential lot for example, one attached ADU inside the home and one detached DADU in the backyard.
No more owner-occupancy requirements. Previously, many cities required the homeowner to live on the property to rent an ADU. That restriction has been removed statewide.
Reduced parking mandates. Cities can no longer require additional parking spaces as a condition of approving an ADU. This is a big deal for smaller lots where parking was previously a dealbreaker.
Reduced fees. Impact fees and utility connection fees for ADUs must now be proportional to the size of the unit not the same flat rate charged for a full-size home. This can save thousands of dollars upfront.
Edmonds and the surrounding Snohomish County area are seeing rapid appreciation in home values and rental demand. Building an ADU or DADU on your property can:
With the new state law reducing barriers, now is an ideal time to explore whether your lot qualifies and what it would take to build.
Costs vary based on size, design, and site conditions, but here are general ranges for the Edmonds and Snohomish County area:
These numbers include permits, construction, and basic finishes. Financing options exist through renovation loans, HELOCs, and ADU-specific lending programs.
We specialize in high-quality home remodeling and construction in Edmonds and the surrounding area. Our team can help you:
We've built a reputation for clear communication, attention to detail, and delivering results that exceed expectations and we bring that same commitment to every ADU and DADU project.
Washington's new ADU laws are a real opportunity for Edmonds homeowners but making the most of it starts with having the right builder in your corner.
Contact Plumb Perfect Builders today to schedule a free consultation. We'll walk you through what's possible on your property, give you a realistic cost estimate, and help you understand the permitting process from start to finish.
Streamlined permitting. Cities are now required to approve ADU permits administratively no public hearings, no discretionary review. If your plans meet the code requirements, it gets approved.
