A yellow house with white windows on a green hill, with a mountain range in the background and cloudy sky above.

Washington State HB 1110

What Changed — and Why It Matters to Property Owners

House Bill 1110 fundamentally changed what can be built on residential land across Washington State.
It redefined single-family zoning by allowing more homes on more lots, in more places, by right.

This was not a density bonus. It was a structural reset of residential land use.

The Core Change

HB 1110 requires most cities to allow “middle housing”—multiple homes on a lot previously limited to one—near transit, jobs, and urban services.

In practical terms, many properties that once allowed one house can now allow:

  • 2 units (duplex) almost everywhere

  • 4 units on most urban residential lots

  • 6 units near frequent transit or with affordability provisions

All without rezoning.

This applies broadly across cities like Seattle, Tacoma, Bellevue, Everett, and many others.

What Counts as “Middle Housing”

HB 1110 explicitly legalizes housing types that were previously restricted or discretionary:

  • Duplexes

  • Triplexes

  • Fourplexes

  • Cottage housing

  • Courtyard apartments

  • Townhouses (with reduced minimum lot sizes)

These are not high-rises. They are low- to mid-scale residential buildings that fit within neighborhood fabric—but change the math.

What Did Not Automatically Change

HB 1110 did not eliminate:

  • Height limits

  • Floor-area limits

  • Setbacks

  • Parking requirements (though many were reduced)

  • Environmental or critical-area regulations

In other words, capacity increased, but feasibility still depends on the site.

This is where most confusion—and most missed opportunity—comes from.

Why This Is a Big Deal for Property Owners

For the first time, residential property value is no longer defined only by what exists today, but by what is legally possible.

That means:

  • A house is no longer “just a house”

  • A backyard may now be buildable

  • A modest lot may support multiple revenue paths

  • Doing nothing can still be the right decision—but it should be an informed one

Every residential property now has to be evaluated as a potential development site, even if it is never developed.

Why Advisory Comes First

HB 1110 created opportunity—but not certainty.

Whether a property should be:

  • Left alone

  • Improved incrementally

  • Reconfigured

  • Redeveloped

  • Sold differently

  • Or simply held and timed

…depends on zoning details, permitting pathways, market conditions, construction realities, and owner goals.

This is precisely where siloed advice fails.

The Bottom Line

HB 1110 expanded what is allowed.
It did not determine what is smart.

Understanding the difference—and deciding when to act, how far to go, or whether to wait—requires a coordinated architectural, land-use, and real-estate perspective.

That is now part of responsible property ownership in Washington State.