Can I Build an ADU on My Property in Puyallup?
In most cases, yes. Puyallup's code allows up to two accessory dwelling units on a single-family lot that meets the zone's minimum size, each up to 1,000 square feet. Washington law bars cities from requiring the owner to live on site.
A few years ago the answer to this question was "maybe, with a lot of conditions." State law changed that. Washington now requires cities and urban areas to allow accessory dwelling units, and it took away several of the rules that used to stop them.
Here is where things stand for Puyallup and the surrounding county.
What state law requires
The Municipal Research and Services Center summarizes the state requirements under RCW 36.70A.680 and 36.70A.681 on its accessory dwelling units page. Cities, and counties in their urban growth areas, must:
- Allow two ADUs per lot in addition to the main house, on lots that meet the minimum size for the main house
- Allow them attached, detached, or one of each
- Allow conversion of an existing structure, such as a detached garage
- Not require ADUs to be smaller than 1,000 square feet
- Not require the owner to live on the property
- Cap impact fees for an ADU at 50% of the fee for the main house
- Not require off-street parking for ADUs within a half mile of a major transit stop
- Not apply setbacks, lot coverage, or entry door rules stricter than those for the main house
- Not ban selling an ADU separately as a condominium solely because it was built as an ADU
Puyallup's rules
Puyallup's ADU provisions are in Puyallup Municipal Code section 20.20.010(11), published at ecode360.com/PU4601. Summaries of that section describe the rules this way:
| Topic | Puyallup rule |
|---|---|
| Where allowed | Single-family RS zones, RS-04 through RS-35 |
| Number | Up to two on a lot that meets the zone's minimum lot area. One on a smaller lot, with some exceptions |
| Maximum size | 1,000 square feet of floor area, not counting garages, workshops, or unfinished storage |
| Bedrooms | Up to three per ADU |
| Detached ADU setbacks | At least 5 feet from rear and interior side lot lines. Front and street-side setbacks follow the zone |
| Separation | At least 10 feet between a detached ADU and the main house |
Confirm the current text and how it applies to your lot with the city's planning staff before you spend money on plans.
If you are in unincorporated Pierce County
A lot of South Hill has a Puyallup address and county jurisdiction. Pierce County's zoning guidance lists ADU size limits of 1,000 square feet inside the urban growth area and 1,250 square feet outside it. A county presentation on its 2025 code updates says urban parcels with a single-family home may have up to two ADUs.
Look up your parcel in the county's About My Property tool to see which jurisdiction and zone you are in.
What can still stop you
The law says ADUs must be allowed. It does not say every lot can fit one. These are the real limits.
Septic. If you are not on sewer, this is the big one. A septic system is sized for a set number of bedrooms. An ADU adds bedrooms. You may need to expand the system or install a second one, and the drainfield and its reserve area take up yard. Talk to the Tacoma-Pierce County Health Department early.
Sewer and water. Even on sewer, connection requirements and fees apply.
Lot shape and setbacks. A detached unit needs 5 feet to the back and side lines and 10 feet from the house. On a small or oddly shaped lot, that may leave no buildable spot.
Critical areas. Steep slopes, wetlands, streams, and floodplains restrict where you can build.
Covenants. Some homeowners associations restrict ADUs through recorded covenants. Read yours.
Access and fire. A unit at the back of a deep lot may need a suitable path for emergency access.
Utilities and easements. You cannot build over most easements.
Types of ADU
| Type | What it is | Typical fit |
|---|---|---|
| Detached | A separate small house in the yard | Larger lots with good access |
| Attached | An addition with its own entrance and kitchen | Lots with room to the side or rear |
| Garage conversion | Turning a garage into a unit | Homes that can spare the garage |
| Basement or interior | A separate unit within the house | Daylight basements, large homes |
| Above garage | A unit over a new or existing garage | Tight lots |
The process
- Confirm jurisdiction and zoning.
- Check utilities. Sewer or septic capacity first.
- Sketch a site plan with setbacks, the drainfield if any, and easements.
- Talk to the permit office before hiring a designer. A short conversation can save thousands.
- Get plans drawn.
- Apply for permits. Building, plus plumbing, mechanical, and electrical.
- Build and pass inspections.
Is it a good idea?
An ADU is expensive to build and recovers only part of its cost at resale. It earns its keep through use: rent, a place for a parent or an adult child, or a home office. I go through the numbers in my post on ADU construction cost.
Two things to keep in mind. A permitted ADU adds to your assessed value, so property taxes go up. And if you plan to rent it, Washington's landlord-tenant rules apply.
Frequently asked questions
Does Puyallup allow ADUs?
Yes. Puyallup's code allows up to two ADUs on a single-family lot that meets the zone's minimum lot area, each up to 1,000 square feet with up to three bedrooms.
Do I have to live on the property to have an ADU?
No. Washington law prohibits cities and urban-area counties from requiring owner occupancy of the main house or the ADU.
How big can an ADU be in Puyallup?
Up to 1,000 square feet of floor area, not counting garages, workshops, or unfinished storage. In unincorporated Pierce County outside the urban growth area, the county lists 1,250 square feet.
Can I build an ADU if I have a septic system?
Possibly. The system must have capacity for the added bedrooms, or be expanded. Check with the Tacoma-Pierce County Health Department before you design.
Related reading
- ADU Construction Cost in Puyallup
- Can I Convert My Garage Into Living Space in Puyallup?
- Can I Subdivide My Property in Puyallup?
- Do I Need a Permit to Remodel in Puyallup?
Thinking about an ADU for family or income? Reach out.
An ADU changes how a property lives and how it sells. If you want to know whether your lot is a good candidate, call, text, or email me.
Austin Robertson
Real Estate Broker, Robertson & Co.
253.225.2395 | austin@robertsonand.co
For people building something worth keeping.
Equal Housing Opportunity. Austin Robertson, License # 21036843, Austin Robertson and Allena Robertson Real Estate Brokers, regulated by the Washington State Department of Licensing (DOL). This article is general information only. It is not legal, tax, insurance, lending, or construction advice, and it is not an appraisal of any property. Costs, rates, and rules change. Confirm the details with the sources linked above before you act.
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