ADU Permits in City of Issaquah

Rules for detached (DADU) and attached (AADU) accessory dwelling units inCity of Issaquah, King County.

Free lookup. We’ll resolve your zoning, setbacks, and which ADU types are allowed on your specific parcel.

Choose an ADU type for your parcel

State law (RCW 36.70A.681) requires City of Issaquah to allow two ADUs on a lot in a single-family zone — one attached and one detached, two attached, or two detached — except on lots with critical areas or their buffers. The per-parcel canvas checks your specific zoning.

DADU — Detached

Backyard cottage with its own foundation and roof. Most flexibility on layout.

See DADU rules in City of Issaquah

AADU — Attached

Basement, garage, or addition conversion inside the primary residence footprint.

See AADU rules in City of Issaquah

Standard Plan

Kolmo has not checked whether City of Issaquah offers pre-approved DADU plans; ask the permit center.

City of Issaquah permit-process facts

Permit department

Submit through the City of Issaquah permit portal.

Permit portal

ADU permit fees

Fee schedule not yet aggregated. Check the City of Issaquah fee schedule directly.

Fee schedule

Review timeline

Typical: 45–120 business days

HB 1337 conformance

City of Issaquah permits at least two ADUs per single-family lot, with no owner-occupancy requirement and parking limits that respect the HB 1337 ceilings.

Building code: 2021 IBC w/ WA amendments · Residential: 2021 IRC w/ WA amendments · Energy (WSEC): 2021 WSEC

Rules above are aggregated from City of Issaquah’s permit-rules table; per-parcel facts (your specific setbacks, easements, ECA buffers) are pulled live on the parcel page. Primary source: https://issaquah.municipal.codes/LUC/18.500.090. Last verified 2026-05-16.

ADU permits in City of Issaquah — FAQ

Does City of Issaquah allow detached ADUs (DADUs)?

Yes. Washington's HB 1337 (RCW 36.70A.681) requires City of Issaquah to allow at least two accessory dwelling units on a lot in a single-family zone within the urban growth area, attached or detached in any combination, except on lots with critical areas or their buffers.

What is the maximum ADU size in City of Issaquah?

State law bars a city from setting a maximum ADU size below 1,000 sq ft of gross floor area (RCW 36.70A.681(1)(f)). City of Issaquah's own maximum may be higher — the per-parcel page shows it with the city's code citation.

How long does ADU permit review take in City of Issaquah?

City of Issaquah's ADU permits typically review in 45–120 business days. Pre-approved standard plans (where available) cut this further.