Renton ADU rules

✓ Verified against code · August 19, 2026

Current rules under RMC 4-2-110C (Renton Municipal Code), adopted by Ordinance 6160 (amended by Ord 6173), in effect since June 16, 2025. Renton adopted its HB 1337 compliance package in June 2025 (Ord 6160) and amended it again five months later (Ord 6173, November 2025) — two rule changes in one year. Its PRADU pre-approved plan program is among the most generous in the state.

Common questions, answered from the code

How many ADUs can I build on a Renton lot, and do I have to live there?

Two ADUs in any mix, and no — no owner-occupancy requirement. Both the house and the ADUs can be rentals. This has been true since Ordinance 6160 took effect in June 2025.

RMC 4-2-110C · Permalink

What is Renton's PRADU program actually worth?

Roughly eight free pre-engineered DADU plans, permits that can issue in about a week, waived plan-review/application fees, several impact fees waived and others reduced — the city estimates around $40,000 in savings. The waiver terms live in the city's fee schedule rather than the municipal code, so confirm current terms with Renton CED before budgeting.

Renton PRADU program; PSRC case study · Permalink

Do I need parking for a Renton ADU?

One space, unless you're within a half-mile walk of a major transit stop — then zero. Lots even partially inside the walkshed count as fully inside.

RMC 4-2-110C fn 20 · Permalink

How big can a Renton ADU be?

1,000 sq ft of gross floor area (and building area). Converting one full floor of your existing house can reach 1,250 sq ft, and PRADU pre-approved plans are exempt from the cap entirely.

RMC 4-2-110C; fns 40–41, 26 · Permalink

Can I convert an existing garage or shed?

Yes, with a major grandfather clause: structures that existed before June 30, 2025 and convert to ADUs are exempt from the lot coverage, setback, and size regulations.

RMC 4-2-110I fn 25 · Permalink

The rules at a glance

ADUs allowed per lot	Two ADUs per legal lot as accessory to a principal dwelling — one attached plus one detached, two attached, or two detached. In the lower-density zones, the second ADU must meet the principal dwelling's location and setback standards.RMC 4-2-110C
Maximum size	1,000 sq ft of gross floor area and 1,000 sq ft of building area (GFA excludes garages, porches, exterior stairs; building area includes attached garages). Converting an entire single floor of the house may reach 1,250 sq ft.RMC 4-2-110C; 4-2-110I fns 40–41, 25
Detached ADU height	24 ft to the highest ridge, with shed-roof averaging allowed. PRADU pre-approved plans are exempt from the height cap.RMC 4-2-110C; fns 23, 42
Detached ADU setbacks	Rear: 5 ft (zero at an alley; a DADU within 10 ft of the rear line must keep 25% of the rear yard's length clear). Side: 25 ft in RC/R-1, 5 ft in R-4 through R-8, 4 ft in R-10/R-14. A detached unit within 4 ft of another residential structure counts as attached.RMC 4-2-110C
Off-street parking	One space per ADU — but zero within a half-mile walking distance of a major transit stop, and lots partially inside that walkshed count as entirely inside.RMC 4-2-110C; fn 20
Owner-occupancy	None. The city confirms both units may be rentals — no on-site owner required.RMC 4-2-110C (absence); city HB 1337 page
Lot coverage / floor area	Zone lot-coverage caps apply; detached accessory structures may exceed coverage by 5%. ADUs are excluded from density calculations. Structures existing before June 30, 2025 that convert to ADUs are exempt from coverage, setback, and size rules.RMC 4-2-110A; 4-2-110I fns 15, 17, 25
Permit path & timeline	Permitted outright — building permit only, no discretionary land-use review. The city states PRADU pre-approved-plan permits can issue in about a week. No street improvements or sidewalks required.RMC 4-2-060; 4-2-080A.7; city PRADU materials

Worth knowing

The PRADU (Permit Ready ADU) program offers roughly eight free pre-engineered plans (about 415–1,000 sq ft), with waived plan-review and application fees plus several impact fees waived outright and others reduced (some utility connection charges are cut ~30% rather than zeroed). City-estimated savings: around $40,000 — confirm current terms with Renton CED, since the waivers live in the fee schedule, not the code.
PRADU plans are exempt from both the size cap and the height cap — that IS in the code.
Renton amended its ADU code twice in 2025; content written between June and November 2025 may already be out of date on details.

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 · Sammamish · Seattle · Shoreline · 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.