Shoreline ADU rules

✓ Verified against code · August 19, 2026

Current rules under SMC 20.40.210 (Shoreline Municipal Code), adopted by Ordinance 1027 (amended by Ord 1043), in effect since January 28, 2025. Shoreline rewrote its ADU section in January 2025 (Ord 1027), then went further than the state ever asked in August 2025: Ordinance 1043 eliminated minimum vehicle parking requirements for everything, citywide.

Common questions, answered from the code

Do I need parking for an ADU in Shoreline?

No — and not because of an ADU carve-out. Shoreline eliminated minimum vehicle parking requirements citywide in August 2025 (Ordinance 1043). Sources describing a one-space ADU requirement predate that repeal.

Ord 1043 §1 · Permalink

How long does a Shoreline ADU permit take?

ADUs are a Type A ministerial decision — staff-level, no public hearing — and the code requires a decision within 65 calendar days of a complete application. Few cities put a number in the code at all.

SMC 20.30.140(A)(1) · Permalink

How many ADUs can I add in Shoreline?

Two per lot, attached or detached, within the zone's units-per-lot density: NR3 allows 3 dwellings per lot (4 near major transit), NR2 allows 4, NR1 has no unit cap.

SMC 20.40.210(A)–(B) · Permalink

How big can a Shoreline ADU be?

1,200 sq ft — above the state's 1,000 floor — and an interior ADU on its own floor under a common roof may exceed even that.

SMC 20.40.210(C) · Permalink

Can I sell a Shoreline ADU separately?

Yes. The 2025 rewrite struck the old ban on separate ownership along with the owner-occupancy covenant requirement.

Ord 1027 §1 · Permalink

The rules at a glance

ADUs allowed per lot	Two ADUs per lot, attached and/or detached — subject to the zone's units-per-lot density (NR3: 3 dwellings per lot, 4 within a half mile of a major transit stop; NR2: 4; NR1: no unit cap).SMC 20.40.210(A)–(B); Table 20.50.020(1)
Maximum size	1,200 sq ft. An ADU inside the residence may exceed the limit if it occupies a separate floor sharing a common roof with the primary home. No garage/storage exclusion is stated in code.SMC 20.40.210(C)
Detached ADU height	No ADU-specific limit — base zone heights apply: 23 ft in NR3 (28 ft with a pitched roof), 30 ft in NR2 (35 pitched), 35 ft in NR1 (40 pitched).Table 20.50.020(1)
Detached ADU setbacks	Side 5 ft; rear 10 ft (NR3/NR2) or 5 ft (NR1); front 10 ft. A DADU's side or rear setback drops to zero where it abuts an alley.Table 20.50.020(1) + Exception (25)
Off-street parking	Zero. Shoreline repealed minimum vehicle parking citywide in August 2025 — not just for ADUs, for everything.Ord 1043 §1; SMC 20.50.390 (repealed)
Owner-occupancy	None. Ordinance 1027 struck the owner-occupancy requirement, the deed covenant, and the ban on selling the ADU separately.Ord 1027 §1 (Exh. A)
Lot coverage / floor area	No building-coverage cap in the NR zones; hardscape is capped at 50% for one unit, rising with unit count (NR3 50% / NR2 60% / NR1 75% for 2+ units). No FAR.Table 20.50.020(1) + Exception (6)
Permit path & timeline	Type A ministerial decision (staff-level, no hearing) plus a building permit — and Type A decisions are due within 65 calendar days, with the clock running from the completeness determination.Table 20.30.040; SMC 20.30.140(A)(1)

Worth knowing

ADUs are a permitted use in every neighborhood-residential and commercial zone.
ADUs may be sold separately from the primary home.
City materials state ADUs pay reduced impact fees and require no street frontage improvements (exact rates live in the fee schedule).
The citywide parking repeal makes Shoreline one of the most parking-permissive cities in the state — for any project, not just ADUs.

On our watchlist

Ordinance 1047 — the '2025 Development Code Batch Amendments' implementing state legislation — was adopted around early 2026; whether it touched SMC 20.40.210 is unverified pending the posted text. We re-check each pass.

ADU impact-fee dollar amounts (fee schedule, Ord 1042) not yet verified.

Check your parcel

The rules above are citywide — what you can build depends on your lot’s zone, size, and setbacks. Look yours up on the official viewers:

Primary sources

Other Washington cities

Bellevue · Bothell · Burien · Edmonds · Everett · Issaquah · Kent · Kirkland · Lynnwood · Olympia · Redmond · Renton · Sammamish · Seattle · Tacoma

Not legal advice. Every fact above cites the code section it comes from — check the cite, or ask your city’s planning department to confirm your specific lot. Spotted an error or a new ordinance? See about to reach us; corrections are logged in the changelog.