Why DADUs Make the Most Sense

By opting for DADUs, you retain the main house and utilize the land far more efficiently.

On a one-acre property, building two DADUs allows for optimal land use, with each DADU occupying a third of an acre, while avoiding the loss of land to Right-Of-Way (ROW) requirements. In contrast, attempting to maximize the unit count with multiplexes results in surrendering nearly half of the property to ROWs and drainage systems like detention ponds. Moreover, the higher density of multiplexes places additional strain on utilities, necessitating costly upgrades to meet the increased demand.

Over the last few years, Washington State has adopted a series of housing bills that are fundamentally changing what homeowners, investors, developers, and neighborhoods can do with residential property.
As a property owner, it’s natural to ask:

“Should I wait to see how these new housing laws might increase my property’s value or create a better return on my investment?”

The answer isn’t always straightforward.

Just as the term “Highest and Best Use” can oversimplify a property’s potential, these housing bills are often misunderstood. Each law was created for a different purpose and comes with its own requirements, limitations, costs, and risks. What works well for one property may not make sense for another.

The most talked-about housing bills include:

• HB-1337: DADU (Detached Accessory Dwelling Unit)
• HB-1110: Middle Housing (Multiplexes)
• SB-5559: Unit Lot Subdivision (Fee Simple Ownership)
• HB-1096: Lot Splitting (Administrative Subdivision – Two Lots)

Understanding the differences between these laws is critical before making decisions based solely on projected property value or development potential. 

SB-5559: Unit Lot Subdivision (ULS)

At first glance, SB-5559 can seem like the perfect solution.

The reason many residential developers are interested in Unit Lot Subdivision is that it allows individual homes within a development to be sold with fee-simple ownership, meaning buyers own their home and lot.

To buyers, this often feels much more like purchasing a traditional single-family home. However, there is an important detail that many property owners don’t initially realize. In many cases, common-interest developments created under a Unit Lot Subdivision still require a homeowners’ association (HOA) to manage shared property, maintenance responsibilities, access easements, utilities, and other community matters. As a result, the developer may still need to establish an HOA structure for the project.

Now, don’t panic when you hear the term “HOA.”

Many people immediately think of large master-planned communities with monthly dues, architectural committees, and extensive restrictions. That’s not necessarily the case. For smaller developments, like the main house with one or two DADUs, an HOA often serves a much more practical purpose:

Protecting multiple property owners who share common interests and ensuring everyone can live together harmoniously.

Imagine owning one of several homes on a property with no governing documents, no rules, and no legal framework for resolving disputes. One neighbor might decide to store oversized vehicles, create nuisances, neglect shared areas, or otherwise impact the value and enjoyment of neighboring properties.

Reasonable HOA bylaws can help prevent bad actors from negatively affecting everyone else who owns property within the development.
At SKYDADU, we assist clients with the legal formation and documentation necessary to properly establish these entities and create governance structures that are appropriate for small-scale housing developments.

HB-1096: Lot Splitting

HB-1096 is often attractive because it can provide a simpler path to creating two lots from one existing residential property.
In some situations, the process may be faster than a traditional short plat because the administrative review process can reduce or eliminate portions of the public hearing process.

That sounds great on paper.

However, many property owners discover that creating two legal lots is only the beginning of the challenge.

Once the lot is divided, the newly created parcels must still comply with a variety of local development requirements, including:

• Building setbacks
• Fire access requirements
• Easements
• Utility corridors
• Critical area restrictions
• Encroachment limitations

As these requirements are applied to each newly created lot, the amount of buildable area can shrink significantly.

The result?

You may successfully create two legal lots yet discover that the newly created lot has very limited space – or in some cases insufficient practical space – to construct a home that meets local requirements. For that reason, lot splitting is not always the straightforward value-add that people initially expect.

So Which Housing Bill Really Threads the Needle?

HB-1337 – Detached Accessory Dwelling Units (DADUs)

After analyzing the practical impacts of these housing bills, we’ve found that one law consistently stands out for homeowners seeking the best balance of cost, flexibility, and feasibility: HB-1337 

HB-1337 provides opportunities that often avoid many of the hurdles associated with traditional subdivision and redevelopment projects.
Compared to other housing strategies, DADUs can potentially offer:

• A simplified and faster approval pathway.
• Zero exposure to subdivision review requirements.
• Relief from many costly frontage-improvement requirements that jurisdictions have historically imposed.
• Greater flexibility in utilizing portions of a property that were previously impossible to develop.
• Lower legal, engineering, and construction costs compared to more complex redevelopment strategies.

Like many multi-owner housing arrangements, projects may still require an HOA or similar governing structure. However, these are often small-scale entities designed primarily to establish ownership rights, maintenance responsibilities, and basic property rules. This is not the same type of HOA many people associate with large subdivisions and expensive monthly assessments. In fact, some small development HOAs may have minimal ongoing responsibilities and limited administrative costs.

The bottom line is simple:

HB-1337 often delivers the greatest amount of additional housing opportunity while creating the fewest obstacles for homeowners.
While every property should be evaluated individually, HB-1337 is frequently the option that provides the strongest combination of affordability, efficiency, flexibility, and return on investment.

That’s why we believe it is the one housing bill that truly threads the needle between homeowner goals, development feasibility, and practical implementation.