Can You Build Two DADUs on One Lot in Tacoma?
We hear this question a lot, and the short answer is yes. Tacoma allows up to two ADU's on a single-family lot, in any combination of attached and detached. But there's more to it - check out this guide we've put together for the details that determine what you can actually do with your Tacoma property.
The Basic Rule
Under current City of Tacoma regulations, a homeowner can add up to two ADUs to a single-family lot as an accessory use to the primary residence, no matter the lot's size or width. In practice that means you can build:
One detached ADU (a DADU) in the backyard
One attached ADU, built into or onto the house
Or both on the same property
This comes from Washington State's HB 1337, which set a statewide minimum requiring cities to allow at least two ADUs per lot in areas zoned for single-family housing. Tacoma's code reflects that state requirement.
What the Fine Print Changes
Two attached units may be treated differently than one. Some city guidance describes two attached ADUs added to an existing home as pushing the structure into a different building code category, with stricter requirements than a single-family home or a single ADU. This is worth confirming directly with the city's permitting office for your specific project, since it affects design and cost. It's also one more reason a lot of homeowners we work with choose a detached unit instead: building detached avoids the question altogether.
Code allows it, but your lot still has to cooperate. The two-unit rule applies regardless of lot size on paper. Septic capacity, utility hookups, existing lot coverage, parking, and the shape of your actual site plan can still rule out a second unit in practice. A lot that qualifies on paper still deserves a real look before you design around two units.
What This Usually Looks Like
Most of the homeowners we build for in Tacoma and Pierce County end up adding one detached DADU behind their existing house. It's the simpler path, and it covers what most people actually need: rental income, space for a family member, or a home office. A true two-unit build, whether that's attached plus detached or two separate detached structures, is possible under the code. It's just a bigger project with more variables, including the building-code question above, and it's worth a real site visit before you assume it'll work on your lot.
Frequently Asked Questions
Can I build two DADUs on one lot in Tacoma? Yes. Tacoma allows up to two ADUs per lot in any mix of attached and detached, under Washington's HB 1337. Whether two units actually fit your lot still comes down to things like utilities, septic, and lot coverage.
Do I have to live on my property to have two ADUs in Tacoma? No, not for standard long-term rental. You can build and rent out two ADUs on regular leases without living on-site.
Can I Airbnb both units on my property in Tacoma? City guidance indicates short-term rental requires the owner to occupy one of the two dwellings, separate from the long-term rental rule. Confirm current requirements with the city before planning around short-term rental income.
Can I sell my DADU separately from my house? This is a genuinely unsettled question under current Washington law and worth asking a real estate attorney directly, since the answer has been shifting and depends on rules specific to your situation.
Does adding two ADUs count as a triplex? Some city guidance treats two attached ADUs differently than one, with stricter building code requirements. Confirm with the city's permitting office for your specific project. Building detached, rather than attached, is one way to avoid the question.
Curious whether your lot can support one unit or two? Get in touch with Tacoma DADU for a free site assessment. We've built 80+ units across Tacoma and Pierce County and can tell you quickly what actually fits.
