Cities · King and Snohomish counties

Can I build a backyard home in Bothell?

Since 2023, Washington law lets most city lots hold up to two more homes. Bothell writes its own rules on top. Here’s what the code says, in plain English — and a free report on what may fit on your lot.

Read from the Bothell code on October 9, 2026 · confidence medium · a summary, not legal advice. Rules change; the report re-reads them for your parcel.

The short version

What Bothell allows.

The headline standards. Open any card for the full wording and the code section.

ADUs per lot2Full wording

2 — 'Two accessory dwelling units are allowed per lot.' One on a lot developed with middle housing; one on lots designated with critical areas or their buffers (BMC 12.14.135.A–C, Ord. 2461, 2025)

Max size1,200 sq ftFull wording

1,200 sq ft — 'An accessory dwelling unit may be developed up to 1,200 square feet.' A conversion of existing space may exceed it with the director's approval, up to 40% of the primary unit's gross floor area (BMC 12.14.135.D.1); DADUs are exempt from the 5%-of-lot accessory-building cap (D.2)

Max height30 ft (33 ft over an existing accessory structure)Full wording

DADU 30 ft; 33 ft over an existing accessory structure — 'Detached accessory dwelling units shall have a height no greater than 30 feet or no greater than 33 feet for units over an existing accessory structure.' (BMC 12.14.135.E); zone maximum 35 ft in R-C/R-L1/R-L2 (BMC 12.14.030 Table)

Front setback15 ft in R-C / R-L1 / R-L2 (20 ft to a garage door)Full wording

15 ft in R-C/R-L1/R-L2 ('All others'); 20 ft to a garage door (BMC 12.14.030 Table)

Side setback5 ft in all residential zonesFull wording

5 ft in all residential zones (BMC 12.14.030 Table)

Rear setback15 ft in R-L1 / R-L2 (0 ft at an alley)Full wording

R-L1/R-L2 15 ft (R-C 35 ft); 0 ft on an alley, 3 ft to alley garage doors (BMC 12.14.030 Table). 'Detached accessory dwelling units shall maintain the same rear yard setback as primary structures,' except on an alley (BMC 12.14.070.B)

Lot coverageHard surface: 55% R-L1, 60% R-L2, 35% R-CFull wording

Maximum hard surface coverage: R-L1 55%, R-L2 60%, R-C 35% (BMC 12.14.030 Table; measured per BMC 12.14.140 — impervious + permeable pavement at 50% + vegetated roofs; no building-coverage percentage). Further limited by BMC Title 14 where critical areas are present

ParkingNone requiredFull wording

None — 'Except as provided herein, there is no required minimum number of off-street parking spaces.' (BMC 12.16.030, Ord. 2461, 2025); the current 12.14.135 has no ADU parking requirement

Where a city figure reads stricter than the state floor (RCW 36.70A.681), the floor may control — the report flags it for your parcel.

The rest

Living there, selling it, plans, time and fees.

Each answer is the code’s own wording, with the section it comes from. “Not published yet” means the city hasn’t posted a figure — the report asks the city, not the internet.

Are backyard homes allowed?

Yes — 'Accessory dwelling units are permitted when added to, created within, or detached from a primary dwelling unit(s)' subject to BMC 12.14.135; 'Dwelling units, accessory' are P in R-C, R-L1, R-L2, R-M1–R-M4 and R-AC (BMC 12.06.140 and condition B.4, Ord. 2479, 2025)

Minimum lot size

None for the ADU. Zone minimum or average lot area: R-L1 6,000 sq ft, R-L2 3,600, R-C 40,000; none in R-M zones (BMC 12.14.030 Table, Ord. 2472, 2025)

Do you have to live there?

No — the current BMC 12.14.135 (Ord. 2461, 2025) has no owner-occupancy provision (the 2019 version's requirement is gone)

Can it be sold on its own?

Not addressed in BMC 12.14.135; the RCW 36.70A.681 floor requires it — confirm the process with the city (HousUp's Lumina Unit C is a Bothell ADU condominium, so the city has processed one)

Pre-approved plans

None found

How long the city takes

City handout 'Permit Processing Timelines' (Development Services, updated 9/25): single-family new construction 4 weeks first review, 2–3 weeks each later review; additions 4 / 2–3 weeks; permit from an approved Basic Plan 3 / 2–3 weeks. 'These times always vary with workload fluctuations. Add one to two weeks, or more, additional review time during high permitting volumes.' No ADU row — a DADU falls under new construction

Impact fees

'The city will not assess impact fees on the construction of accessory dwelling units that are greater than 50 percent of the impact fees that would be imposed on the principal unit.' (BMC 12.14.135.G). Park (BMC 21.08), school (21.12) and fire (21.16) impact fees apply; amounts not read

Your lot

The code is half the answer. Your parcel is the other half.

Lines and easements

Where the lot lines really are, which setbacks apply on each side, and whether a utility or access easement takes the corner you had in mind.

Critical areas and slope

Steep slopes, wetlands and streams come with buffers that no citywide number shows. The report reads the county’s maps for your parcel.

Sewer, septic, water, trees

Whether sewer reaches the lot or it’s on septic, where the water service is, and which trees a city protects — the things that decide where a unit can actually go.

Free, within a few hours, no obligation.
What Bothell allows, what could fit on your lot, and a planning cost range. If something won’t fit, the report says so — and shows what might.

Check my property, free →

Sources

Where this page comes from.

Read from the Bothell municipal code and the city’s own pages on October 9, 2026. The same table feeds the HousUp report, so the report and this page never disagree. Cities amend their codes; before you design anything, confirm the current wording with the city.

Find out what your property could become.

Type your address. Within a few hours: what Bothell allows, what could fit, and a planning cost range. Free, no obligation.

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