Understanding House Bill 1110 — The Law That Changed Everything

[Tim Cornwell]

Understanding House Bill 1110 — The Law That Changed Everything

"Washington is in the midst of an affordable housing and homelessness crisis."
— Washington State Department of Commerce, 2024–2029 Homeless Housing Strategic Plan

In 2023, Washington passed one of the most transformative housing laws in its history: House Bill 1110.

This new law makes it legal to build duplexes, triplexes, and fourplexes in areas that were previously reserved for single-family homes — unlocking a wave of possibility for homeowners, investors, and the future of housing in our state.

🧱 What Does House Bill 1110 Do?

House Bill 1110 requires cities to allow middle housing types — like duplexes, triplexes, and fourplexes — in residential zones that historically restricted development to single-family homes.

Here’s how it works:

• ✅ Cities over 75,000 people must allow:

  • Fourplexes on all residential lots

  • Sixplexes if two units are affordable or near frequent transit

• ✅ Cities between 25,000–75,000 people must allow:

  • At least duplexes on all residential lots

This means that in much of Washington, the average residential lot has the potential to legally support more housing types, often without requiring a rezoning process.

🔑 Why It Matters

This isn’t just a zoning change — it’s a paradigm shift.

Here’s why it matters:

• 🏘️ Unlocks More Housing Options: Legalizes a variety of home types to suit different household sizes and incomes.

• 💰 Promotes Affordability: Smaller housing units typically cost less to build and buy, helping close the affordability gap.

• 🚶 Enhances Walkability: Encourages infill development near transit, parks, and schools — making communities more connected and livable.

• 🌿 Supports Sustainable Growth: Concentrates development where infrastructure already exists, limiting urban sprawl and preserving open space.

• 🔧 Streamlines Development: Reduces red tape and accelerates housing creation by simplifying local permitting processes.

• 🚗 Modernizes Parking Requirements: Relaxes minimum parking standards for projects near public transit, helping cut costs and promote alternative transportation.

• 🏗️ Empowers Local Builders and Homeowners: Gives everyday homeowners and small developers the chance to invest and build in their neighborhoods.

• 📈 Addresses the Housing Shortage: Part of the broader goal to build over 1 million new homes in Washington by 2044.

💼 What This Means for Homeowners and Investors

House Bill 1110 opens the door to real opportunity — not just for policy makers or city planners, but for you.

Whether you're:

• A homeowner looking to build a duplex in your backyard,

• An investor considering a fourplex conversion,

• Or a small-scale builder exploring infill development...

This law gives you a new legal framework to create housing, equity, and lasting community value.

🧭 Want to Know What’s Possible on Your Lot?

Every city is implementing HB 1110 differently, and local conditions vary — but I can help you navigate:

• 📐 Zoning & permitting

• 💡 Site layout and design ideas

• 💰 Feasibility and profit strategies

• 🏡 Exit strategies: rentals, resale, or condos

📌 Coming up next: How Condominiumization Can Multiply Your Returns Under Washington's New Housing Laws

Let’s connect if you're curious about what your property could become.

[Nik Moushon]

@Tim Cornwell

I'm with Jay on this. Its not going to move the needle much at all. Yes, its great for in-fill lots that are currently empty or have a house that needs to be pushed over already. 

The big hurdles that are preventing this from really making an impact are:

1) Barrier to entry cost - This is all the permit fees, environmental studies, professional costs, etc. These costs are so high, and time consuming, that the vast majority of people that would like to do these small developments on 1-4 units, can't make the numbers work. They need tens of thousands of dollars cash (sometimes hundred thousand plus) just to get to the point where they can submit a building plans for review. With small 1-4 units, its near impossible to get a bank loan until you have that all complete and permits approved. So yes the owner can get most of those costs back in the loan but they have to floar that cash for at minimum a year, if not more. Then does recouping those up front soft costs make the final numbers very difficult to cash-flow? 

2) Most towns, especially the smaller ones in the 25k-75k range, do not have a short plat processes for allowing small lots that could be peeled off from the parent lot of a single family home. This make financing difficult and also limits your options on if you can sell just the new building or have to sell the parent house with it. Also, the older style "flag lot" is not allowed in most jurisdictions, and land locked properties aren't either. This limits a good portion of SFH lots that only have access from one side as not being feasible without tearing down a portion of the main house.

3) Most existing single family homes do not have the room (square footage) to subdivide the lot. Which means you are forced to turn the SFH into multiple units and/or add a ADU. This is relatively new, so data is still being compiled, but from some of the reports I've seen, the cost of the conversion and/or adding an ADU is more than the new appraised value with multiple units on it. This circles back to financing issues.

I only say this to push back against the narrative that this will fix the housing problem. Not that you can't make money on an in-fill development. Lots that work with this new 'middle housing type' codes are far and few between in most places. I've done this exact thing and have amazing returns with that development. My biggest thing is the zoning reform is one step in the right direction but the barrier to entry for doing these developments is still so high that 95% of the lots that have this potential are not going to get developed because the owners don't see enough return for the money and effort it takes to do this.