The Real Story Behind the Middle-Housing Wave

by Cheryl Dillon

The Real Story Behind the Middle-Housing Wave

Washington’s housing map is being redrawn—quickly. Since the Legislature passed HB 1110 in 2023 (and follow‑ups in 2024–25), city after city has been rewriting code to allow duplexes, triplexes, fourplexes and cottage courts where only detached houses once stood. So…how many places have actually done it?

Rather than a neat, final tally, we have a moving target. Cities are adopting ordinances on rolling deadlines tied to population size and transit access. Some have fully removed “single-family” as a zoning category (Edmonds, Seattle, Bellingham, Spokane, Olympia and others). Many more have technically kept the label but now must allow multiple units on every “single-family” lot—functionally ending exclusive single-family zoning even if the name lingers.

Why the number keeps changing

Staggered deadlines. Larger Puget Sound cities had earlier compliance dates; smaller jurisdictions have more time.
Different approaches. Some councils passed comprehensive rewrites; others layered middle housing on top of existing zones.
Tweaks after adoption. Initial ordinances often get follow-up fixes—parking, lot splits, design standards—so “adopted” isn’t always “finished.”

What matters more than the headline count

1. Depth of permission.
Did the city simply allow duplexes, or did it also greenlight fourplexes, lot splits, courtyard clusters, and small multiplexes? The broader the menu, the more meaningful the reform.

2. Barriers removed (or not).
Parking minimums, minimum lot sizes, height caps, and cumbersome design review can quietly undermine the promise of middle housing. The strongest ordinances trim those frictions.

3. Speed to permits.
Paper reform isn’t housing. Fast, administrative approvals (not years of hearings) will determine how many homes get built.

Cities to watch

Edmonds: Recently scrapped its RS (single-family) zones outright and is now layering on “Neighborhood Centers & Hubs.”
Seattle: Interim rules already allow 4–6 units on former SF lots, with permanent code on the way.
Spokane & Bellingham: Early movers that paired middle housing with parking reform.
Tacoma & Olympia: Comprehensive rezones plus streamlined permitting.
Kirkland, Redmond, Everett, Bothell: Each is adjusting code and parking to meet state mandates while aiming to preserve neighborhood character.

The builder’s checklist (and homeowner’s too)

Know your lot. What’s now allowed? Duplex? Fourplex? Cottage court? Lot split?
Watch design standards. Roof pitches, materials, setbacks—these details can make or break feasibility.
Mind parking + infrastructure. Cities easing parking can lower costs, but utilities, sidewalks, and stormwater still need attention.

So, how do you talk about it?

When clients ask, “Is single-family zoning gone?” try this:

“Exclusive single-family zoning is on its way out across Washington. Many cities have already opened every lot to more homes—others are finalizing the rules. The real question is less ‘if’ and more ‘how much’ and ‘how fast.’”

Final Take

The precise count will always lag reality. What’s certain is momentum: Washington is transitioning from an era of exclusionary zoning to one of gentle density. If you’re a homeowner, buyer, builder, or investor, now’s the time to learn what your city passed, what’s coming next, and how to leverage the new rules—before everyone else figures it out.

#middlehousing #urbanplanning #affordablehousing #zoningreform #communitydevelopment

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Cheryl Dillon

+1(425) 954-5622

cheryl.dillon@exprealty.com