Condo vs. Unit Lot Subdivision: How to Split a Seattle Lot Under Middle Housing (FAQ)

Our post on the new middle housing rules is still one of the most-read things on our site, and it’s fair to say it’s the reason our phone hasn’t stopped ringing. Everyone wants to know some version of the same thing: I have a single-family lot, I can apparently put multiple homes on it now, so how do I actually divide it up so people can own their piece separately?

We sat down with Terrance Wilson, a Seattle land use attorney who’s been doing subdivisions and land surveying since 1996, to walk through the two tools that actually make that possible: condominiumization and unit lot subdivision (ULS). This post is the FAQ that came out of that conversation.

A quick note before we start: this is general information, not legal advice for your specific property. Talk to a land use attorney before you record anything.

Why can you even do this now?

For most of Seattle’s history, single-family lots had minimum size requirements — historically 5,000 square feet — that made it hard to fit more than one house on a typical lot. Washington’s statewide middle housing law changed that. Under Seattle’s current zoning (SMC 23.44.060), a standard lot allows up to four homes, and a smaller lot near frequent transit allows up to six.

In effect, the city took single-family zones and made them multifamily zones. Everything below is built on concepts land use attorneys have used in multifamily zones for decades. None of it is new. It’s just newly available on your street.

Do I have to subdivide my lot to build multiple homes on it?

No. This is the part people miss most.

You can get a building permit for three, four, five, or six homes on one lot and simply never divide it. You’d own all of them, rent them out, and that’s it. No HOA, no CC&Rs, no subdivision process.

Your permitting is based on your lot as it exists today, not on how you plan to divide it later. Subdividing — via condo or ULS — is something you opt into, usually because you want to sell homes individually, get separate financing, or hand a piece of the property to a family member.

What’s actually different about the two ways to divide?

Both a condo and a unit lot subdivision create lines of ownership, not new independently buildable lots — Seattle’s code says so directly: a unit lot “is not a lot” (SMC 23.22.062 / 23.24.045, and the Title 23 definitions of “Lot, parent” and “Lot, unit”). Whichever path you take, your permitted density and square footage are still measured against the whole original lot, not the individual pieces.

Unit lot subdivision is a municipal process, governed by that same section (SMC 23.22.062 for most zones, 23.24.045 for others). You submit it to the city, it goes through public review, and neighbors get two chances to weigh in — once at application, once at conditions of approval — in front of a hearing examiner. In Seattle, that process typically takes six months to a year, sometimes longer.

Condominiumization isn’t municipally reviewed at all — it’s created under Washington’s Condominium Act (RCW 64.34), not Title 23. It’s a private legal instrument, prepared by an attorney and a surveyor, recorded directly with the county. That means you control the timing entirely. Some owners record a condo declaration before they’ve even submitted a building permit. Others wait until permit plans are approved, so the recorded boundaries actually match what gets built.

The trade-off: ULS gives you city-reviewed certainty, but it’s slower and opens your project up to neighbor appeals. Condo gives you speed and control, but skips that review — which matters more than you’d think once financing enters the picture (more on that in our next post).

Do my co-owners or neighbors need to approve my building permit?

No jurisdiction has required this so far. Even though your piece of the lot is a fractional share of a larger site that other people also own, the building department only requires the applicant’s signature.

That said, good CC&Rs should still plan for it. Two clauses are worth having in there from day one: language that keeps a co-owner from holding your project hostage, and a requirement that co-owners cooperate on paperwork the city might ask for later. Neither is required by code. They exist because attorneys like Terrance have seen enough of these projects to know what gray areas can turn into problems, and it’s cheap to close the gap early.

Do I need an HOA?

Depends which path you take. A condominium always requires one — it’s built into the process. A unit lot subdivision doesn’t automatically require one, though certain situations can trigger it.

Either way, you’ll need CC&Rs and easements regardless — for shared driveways, party walls, trash and parking, and the inevitable “what color can I paint my door” questions. If you’re doing a unit lot subdivision, EV charging easements specifically are called out in the code (SMC 23.22.062.D).

How do shared utilities actually get handled?

This comes up on almost every project. For something small and shared — an irrigation pump, exterior lighting — the simplest approach is to have that bill run through whichever owner’s unit the equipment sits on. It’s a few dollars a month, and it saves everyone from prorating a tiny bill. If that equipment ever needs major repair, that cost gets shared the way a driveway repair would.

EV charging usually goes one of two ways: wired directly to the owner’s own meter, or run to a shared “house meter” with an app that tracks and prorates usage. Both work fine — it’s a matter of what your CC&Rs spell out.

So which one should I use?

There’s no universal answer. It depends on your timeline, your risk tolerance, and — this is the big one — your existing financing.

If you want city-reviewed certainty and don’t mind the wait, ULS is the more conservative path. If speed and control over timing matter more, condo is usually faster, provided you’re comfortable recording before your site plan is fully locked.

Either way: talk to your lender before you record anything. In our next post, we get into why — including a real example of a lender calling a loan due after a client condominiumized without telling them first.

Code references, if you want to go straight to the source

• SMC 23.44.060 — density and minimum lot size (4 units per lot; 6 near frequent transit)
• SMC 23.22.062 / 23.24.045 — unit lot subdivisions, including the EV charging easement requirement in 23.22.062.D
• Title 23 definitions — “Lot, parent” and “Lot, unit” (a unit lot is not a lot)
• RCW 64.34 — Washington Condominium Act, which governs condo declarations instead of Title 23

Current as of Seattle’s permanent Neighborhood Residential zoning, effective January 21, 2026.

Have a Seattle infill project you’re working through? We’d love to help you think it through — contact us to start the conversation. Thanks to Terrance Wilson for the deep dive this post is built on.

Related: Digging into ADU and DADU Zoning Updates | Is a DADU Right for Your Seattle Home?