Washington's housing laws offer two distinct paths forward. The differences — in cost, financing, community impact, and long-term value — are substantial, and they decide which path actually works on a lot you already own.
The housing laws passed in Washington State may sound similar, but the differences between them — especially in terms of cost, community impact, and long-term value — are substantial. HeartLink Homes is here to help you understand these distinctions and make informed decisions about your property's future.
Middle Housing Law (HB 1110) is mainly for developers. DADU Law (HB 1337) allows homeowners to be the developers. You can profit without buying or subdividing your lot.
Both laws increase density. Only one of them is written in a way an individual homeowner can realistically use.
What it permits:
The reality:
What it permits:
The benefits:
Ten factors that separate a multiplex project from a DADU project on the same piece of land.
| Factor | HB 1110 (Multiplex) | HB 1337 (DADU) |
|---|---|---|
| Target Audience | Developers seeking maximum density | Homeowners building generational wealth |
| Main House | Demolished | Preserved |
| Neighborhood Impact | Incongruent tall structures | Harmonious architectural integration |
| Historic Preservation | Destroys history | Preserves history and character |
| Right-of-Way Requirements | Often required (major cost increase) | Prohibited by law (major cost savings) |
| Infrastructure Upgrades | Sidewalks, utilities, drainage systems | Minimal requirements |
| Financing Availability | Challenging (often requires commercial loans) | Traditional mortgages available |
| Housing Type | "Affordable" housing (subsidized programs) | "Attainable" housing (market-rate quality) |
| Return on Investment | Lower over time (units harder to fill/sell) | High (8–10%+ cash-on-cash returns) |
| Community Reception | Often opposed by neighbors | Generally embraced by community |
Comparison reflects typical outcomes under HB 1110 and HB 1337 as implemented by Washington jurisdictions; specific requirements vary locally. The cost, financing, and return figures in this table are reported by our building partner from their completed projects — HeartLink Homes is a real estate brokerage, not a builder or lender, and does not verify or guarantee them.
The visual impact on your neighborhood is one of the most striking differences between these two approaches.
HB 1110 multiplexes have been linked to numerous challenges including overcrowded parking and adverse impacts on neighborhoods. But one significant concern stands out: the demolition of homes that have held historical significance within the community for decades.
The HB 1110 legislation permits construction of multiplexes and higher-density structures in neighborhoods traditionally zoned for single-family homes. The result:
"You're destroying the history of Seattle. Please don't." — actual community member testimony
The HB 1337 DADU legislation permits homeowners to build up to two separate units on their property. The advantage:
"DADUs allow the main house to remain intact while adding units that seamlessly blend with its architectural style."
Multiplexes destroy the history. DADUs preserve the history. This isn't just about housing — it's about maintaining the character and architectural fabric of established neighborhoods.
At first glance, building multiplexes might seem appealing — more units means more rental income or sales, right? Not so fast. The economic reality tells a very different story.
Cities can impose expensive sidewalk construction, street improvements, and public infrastructure upgrades.
Higher density strains existing utilities, necessitating costly upgrades to meet increased demand.
Often required to build detention ponds and comprehensive drainage, consuming valuable land.
Up to half of your property surrendered to ROWs and drainage — land you can't use or monetize.
Often requires commercial construction loans with higher rates and stricter terms.
Cramped buildings with high occupancy deter buyers and renters, leaving units unsold or vacant.
On a one-acre property, attempting to maximize unit count with multiplexes results in surrendering nearly half of the property to Right-Of-Way requirements and drainage systems. The final units often remain unsold or unrented, resulting in financial strain.
HB 1337 prohibits local governments from requiring public street improvements, sidewalks, or ROWs.
Keep your main house and utilize land far more effectively — each DADU occupying optimal space.
Significantly reduced expenses translate to better financial returns.
Traditional mortgage products available for both owner-occupied and non-owner-occupied properties.
8–10%+ returns from passive rental income.
High-quality, single-family residence appeal with yard space attracts premium buyers and renters.
On a 1/3 acre lot: You can keep your main house and add two DADUs, each occupying a third of an acre, with no land lost to ROWs. This maximizes your property value and rental income while avoiding the massive infrastructure costs multiplexes require.
ROI comparison: DADUs deliver over 180% return on investment in some areas, while multiplexes often struggle with lower returns due to high construction costs and marketability challenges.
Construction cost and return figures in this section are reported by our building partner from their completed DADU projects. They are illustrative, not verified or guaranteed by HeartLink Homes, and not a projection for any specific property.
When you listen to community members at town hall meetings, a clear pattern emerges: neighborhoods don't want their historic character destroyed. The backlash against HB 1110 multiplexes has been significant across Washington State.
About multiplexes (HB 1110):
Why DADUs work for communities:
DADUs represent a thoughtful approach to increasing housing availability while respecting the historic fabric of our communities. They add housing capacity without destroying the homes and character that define a neighborhood.
The two laws produce different products, aimed at different points in the market.
| Category | HB 1110 Multiplexes | HB 1337 DADUs |
|---|---|---|
| Primary Beneficiaries | Developers seeking maximum density | Homeowners, investors, and trusts that own the underlying lot |
| Housing Type | "Affordable" housing (subsidized programs) | "Attainable" housing (market-rate, high quality) |
| Typical Buyer Financing Profile | Entry-level purchase price point, with little to no cash down payment | Move-up price point, with substantial down payments |
| Closing Certainty | May be challenging (financing hurdles) | Fairly certain (buyers have resources) |
| Unit Quality | Basic, high-density living | Single-family residence quality with yard |
| Investment Returns | Less ROI over time (unsold units common) | High ROI and cash-on-cash returns over time |
Return, cost, and financing characteristics in this table are reported by our building partner from their completed projects; statutory provisions are drawn from HB 1110 and HB 1337.
Eight reasons the HB 1337 path outperforms the HB 1110 path for someone who already owns the land.
You become the developer, profiting without buying or subdividing additional lots.
Move into your DADU later in life while renting or selling the main house — far less cost than senior living facilities.
Rental income for you and future generations, plus the HB 1217 rent control exemption for 12 years from construction.
Build assets your children and grandchildren can inherit.
Multiplexes destroy history; DADUs preserve it.
Maintain the established character of a neighborhood while adding housing.
Rent for income, sell as condos for profit, or use for family — multiple options.
Traditional mortgages available versus challenging commercial loans for multiplexes.
We don't just sell construction — we educate you on your options. We help you understand what's possible on YOUR specific property, navigate the differences between HB 1110 and HB 1337, and connect you with the right resources.
Most importantly: We partner with an award-winning design-build firm that specializes in DADUs designed to complement your existing home and neighborhood.
The contrast between multiplexes and DADUs becomes crystal clear when you see real examples of how these structures impact neighborhoods. DADUs maintain the aesthetic harmony of established communities, while multiplexes often create jarring visual disruptions.
Imagine your street today: historic homes with character, mature trees, cohesive architectural styles. Now picture a three-story multiplex towering over neighboring properties, casting shadows, with multiple units facing into yards that once enjoyed privacy.
This is the reality communities across Washington are facing with HB 1110 multiplex development.
Contrast this with a well-designed DADU: it complements the main house, uses similar materials and architectural elements, fits the scale of the neighborhood, and provides quality housing without destroying the character that made the area desirable in the first place.
This is the thoughtful approach that communities embrace.
HeartLink Homes specializes in helping homeowners navigate the DADU path — not multiplex development. We'll show you what's possible on your specific property under HB 1337, compare the financials against multiplexes, explain how DADU-specific financing generally works, and introduce you to our building partner — who handles the design, financing, permitting, and construction.
Our role: HeartLink Homes is a licensed real estate brokerage. We are not a builder, a contractor, or a lender. Design, construction, and financing are handled by our building partner. Any construction cost, timeline, financing, or return figure on this page is reported by that partner from their own projects — it is not verified, offered, or guaranteed by HeartLink Homes, and it is not a projection of what your property will do. Our role is education, referral, and real estate representation if you later sell a DADU or your main house.
This side-by-side comparison of Washington's two 2023 housing laws was created by HeartLink Homes at Keller Williams Realty Puyallup. Information has been compiled from:
Important: This page is general education, not legal, tax, financial, or investment advice. Cost, return, and ROI figures are illustrative and vary widely by property, jurisdiction, design, and market conditions — they are not a guarantee or projection for your property. 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.