The context behind HB 1110 and HB 1337 — why Washington rewrote its housing rules in 2023, and why one of those two laws puts homeowners, not developers, in the driver's seat.
Before diving into the specific opportunities that Detached Accessory Dwelling Units (DADUs) present, it's worth understanding the broader context: Washington State is facing a housing shortage that affects every community, every family, and our collective future.
The legislation we'll discuss — HB 1110 (Middle Housing) and HB 1337 (DADU Law) — didn't emerge in a vacuum. These laws represent a comprehensive legislative response to one of the most pressing challenges of our time: how to provide housing for a growing population while maintaining community character, preserving affordability, and creating pathways to wealth-building for everyday homeowners.
Washington State faces a housing shortage that has been decades in the making, and the numbers tell a sobering story.
Washington needs approximately 1,000,000 new homes by 2044 to meet the housing needs of our current and future population. That isn't just about raw numbers — it's about people. Families struggling to find housing they can afford. Young professionals unable to buy a first home. Seniors seeking to age in place. Essential workers commuting hours because they can't afford to live near their jobs.
Washington's population continues to grow steadily, driven by job opportunities, quality of life, and migration from other states. Housing production has not kept pace with that growth.
For decades, most residential areas were zoned exclusively for single-family detached homes, limiting housing diversity and restricting supply in established neighborhoods.
The shortage of housing has driven prices to historically high levels, pricing out middle-income households and creating affordability challenges across the state.
Washington is unlikely to meet affordability goals for future populations without changes to housing policy. The state needed a multi-faceted approach that would:
Washington's legislature passed two landmark housing laws in 2023, both taking effect in 2024 after jurisdictions completed their comprehensive plan updates and development regulations.
House Bill 1110, passed in 2023, changed how Washington approaches housing density. The law requires cities to allow "middle housing" — housing types between single-family homes and large apartment buildings — throughout areas previously zoned exclusively for single-family homes.
The legislation addresses affordability in several ways:
The practical reality: HB 1110 is primarily used by professional developers and builders who have the capital, expertise, and scale to undertake multiplex developments. This law created opportunities for the development community to address the housing shortage.
While HB 1110 opened doors for professional developers, House Bill 1337 (also passed in 2023) took a different approach: empowering individual homeowners to become developers of their own property through Detached Accessory Dwelling Units.
This legislation recognized that not every solution to the housing shortage needs to come from large-scale development. Individual homeowners, collectively, control vast amounts of residential land. By enabling these property owners to add housing units to their existing lots, HB 1337 unlocks a distributed source of new housing supply.
HB 1337 changes the equation for homeowners:
Both laws aim to increase housing density, but their effects on existing neighborhoods are very different.
The typical pattern:
Many neighborhoods have opposed HB 1110 developments, citing concerns about losing neighborhood history, character, and charm as century-old homes are replaced with modern multiplexes.
The DADU pattern:
DADUs are generally better received by communities. They add housing density while preserving the older homes and architectural character that define a neighborhood.
Bottom line: HB 1110 multiplexes often replace the existing housing stock. HB 1337 DADUs add to it — reaching density goals without erasing what's already there.
HB 1337 lets homeowners contribute meaningfully to Washington's housing density goals while maintaining community character.
Instead of concentrated developments in specific areas, DADUs create housing throughout established neighborhoods. This spreads the benefits — and the infrastructure load — more evenly.
DADUs use existing urban infrastructure — streets, utilities, transit, schools, and services. That's far more cost-effective than extending infrastructure to greenfield development on the urban fringe.
By adding housing in established areas, DADUs reduce sprawl, preserve natural lands, shorten commutes, and support climate goals — while being more energy-efficient than larger homes.
Washington needs 1,000,000 new homes by 2044 — approximately 50,000 homes per year. If even a fraction of existing homeowners added DADUs:
The power of HB 1337 is in its scale: thousands of individual property owners, each making a modest addition, collectively creating significant housing supply — while preserving the character of their neighborhoods.
The two laws address cost in different ways, and the vocabulary matters.
| HB 1110 — "Affordable" Focus | HB 1337 — "Attainable" Solution | |
|---|---|---|
| Definition | Income-restricted units, often subsidized through government programs, with eligibility requirements and below-market rents | Market-rate housing accessible to working households — not subsidized, but reasonably priced through efficient design and construction |
| Who builds it | Professional developers with capital and scale | Individual homeowners on lots they already own |
| Practical reach | Projects can include affordable units, but market-rate units in multiplexes may still be priced beyond reach for many middle-income households in high-cost markets | Smaller, well-designed units that rent or sell at prices middle-income households can manage — quality housing within reach rather than affordable by subsidized definition |
Terminology as used in Washington housing policy discussion; see HB 1110 and HB 1337 statutory text for legal definitions.
Washington's housing challenge requires solutions at every scale — from state policy to large developments to individual homeowner action.
HB 1337 recognizes that everyday homeowners have a role to play. By enabling you to become a developer of your own property, the legislation creates a genuine opportunity: you can help address a community need while building wealth for your family.
This is the power of HB 1337: it turns homeowners from observers of the housing shortage into participants in the response — while creating financial opportunities that benefit their families for years.
Understanding the 30,000-foot view is worth the time, because it clarifies four things.
Washington's housing shortage isn't a distant problem — it's affecting households right now. Every year that passes without adding housing, affordability gets harder and more people are priced out of ownership and stable housing.
HB 1337 represents an unusual opening for homeowners. The legal framework, financing options, and market conditions currently align in a way that creates real possibilities for wealth-building and community contribution.
You have a say in how density arrives in your neighborhood. Support for DADUs means housing growth that preserves the existing streetscape. Opposition leaves the field to HB 1110 developments that change neighborhoods more visibly.
Individual homeowner decisions add up. If thousands of homeowners each add one or two DADUs, the combined effect on housing supply is significant — achieved incrementally, preserving neighborhood character.
We'll walk you through a property-specific analysis, the financing options that fit your situation, and an honest picture of what the process involves — before you commit to anything.
This overview of Washington's housing legislation was created by HeartLink Homes at Keller Williams Realty Puyallup to give homeowners the context behind the DADU opportunity. Information has been compiled from:
Important: This page is general education, not legal, tax, or financial advice. DADU rules are implemented locally, and requirements for lot size, height, setbacks, parking, and permitting vary by jurisdiction and change over time. Verify current requirements with your city or county planning department before making decisions. Contact HeartLink Homes to discuss your specific property.