Detached ADU (DADU) Permits in Lynnwood

A standalone backyard cottage with its own foundation, roof, and exterior. Maximum flexibility on layout; highest construction cost. State law bars a city maximum below 1,000 sq ft of gross floor area, except on lots with critical areas (RCW 36.70A.681).

Free lookup: your lot’s zoning and setbacks, with a detached ADU placed on it to move and turn.

Permit fees in Lynnwood

Set by the Lynnwood fee schedule.

Lynnwood fee schedule

Lynnwood prices an ADU's building permit on the value of the work, by the ICC valuation table or the square footage, whichever is greater: $1,181.86 for the first $50,000 plus $12.62 for each $1,000 more up to $100,000, and $1,812.71 for the first $100,000 plus $10.32 for each $1,000 more up to $500,000. Plan review is 65% of that fee. For new construction, the plumbing and mechanical permits are each 10% of the building permit fee; in an addition they are $257 for up to 4 fixtures or pieces of equipment and $22 for each one more. The City issues the electrical permit, priced for new construction on its electrical valuation table, $114 up to $1,000. A 2.5% technology fee is added (LMC 3.104).

Review timeline

Not published by Lynnwood.

What Lynnwood asks for with a detached ADU

Every application (19)

ADU permit (land use application), approved and recorded before the building permit
Residential building permit application (combo permit: building, mechanical, plumbing), after the ADU permit
Project narrative, with the owner-occupancy statement
Owner-occupancy affidavit and the ADU permit, recorded with the Snohomish County Auditor
Site address
Snohomish County parcel number
Site plan, in the plan set
ADU entrance, its added parking, and the no-separate-sale statement, on the site plan

The other 11

13-Element Checklist, or a SWPPP at 2,000 sq ft or more of land disturbance
Foundation plan
Floor plan
Roof + floor framing plan
Typical building / wall section
Building elevations N/S/E/W
Glazing + door schedule (NFRC U-factor / SHGC)
Structural design notes (loads, materials, inspections)
Major materials schedule
Energy code and whole house ventilation information, on the plans
Energy code supporting calculations and worksheets

Where the lot or the work calls for it

Where the lot is in a landslide hazard area or is in a seismic hazard area

Geotechnical report

From the city’s own documents: City of Lynnwood Development & Business Services — Accessory Dwelling Unit (ADU) Submittal Checklist (June 2022) · City of Lynnwood Development & Business Services — Residential Permit Checklist (New Construction & Additions) (June 2024) · Lynnwood Municipal Code 21.42.110(G), Accessory Dwelling Units, last read October 22, 2026. An address’s own page checks its lot for slopes, flood zones and critical areas.