Seattle Permit Guide · 2026

ADU / Garage Conversion Permits
in Seattle, WA

Permit fees for a ADU or garage conversion in Seattle typically run $1,075–$4,300. Here's exactly which permits you need, what they cost, and how long WA review takes.

Do you need a permit for a ADU or garage conversion in Seattle?

Always — converting space into a dwelling unit triggers full plan review, zoning approval, and utility sign-offs in Seattle. Permit fees for a typical $214,448 ADU or garage conversion run about $1,075–$4,300 (valuation-based fee plus plan review), and WA plan review typically takes 3–6 weeks.

Permits you'll likely need

Building

full plan review for the dwelling conversion

Zoning / occupancy

ADU ordinance compliance and occupancy approval

Utilities

sewer, water, and electrical service connections

Fire / egress

separate egress and smoke/CO requirements

Usually exempt

Nothing meaningful — every part of a ADU or garage conversion runs through permitting. Budget for it up front.

WA permit note

Energy Code Requirements: Washington has strict energy codes that exceed national standards Washington energy code requires high insulation values and air sealing. Reddit users note that meeting code adds cost but significantly reduces heating bills.

How to get ADU or garage conversion permits in Seattle

1
Confirm what triggers a permit
Building, Zoning / occupancy, Utilities, Fire / egress permits apply when the scope includes full plan review for the dwelling conversion. Cosmetic-only scopes may be exempt.
2
Budget the fee
Plan for $1,075–$4,300 in Seattle — a valuation-based fee on a typical $214,448 project plus plan review.
3
Apply with complete documents
Submit scope, drawings, and contractor license info to the Seattle building department. WA plan review typically takes 3–6 weeks.
4
Verify it in the bid
A complete Seattle bid lists permit fees as a line item. If a bid omits permits — or suggests skipping them — analyze it before signing.

ADU / Garage Conversion permits in Seattle: FAQ

Do I need a permit for a ADU or garage conversion in Seattle?

Always — converting space into a dwelling unit triggers full plan review, zoning approval, and utility sign-offs in Seattle, WA. When in doubt, call the Seattle building department before work starts — unpermitted work can block a future sale.

How much do ADU or garage conversion permits cost in Seattle?

Expect roughly $1,075–$4,300 in Seattle for a typical $214,448 ADU or garage conversion. Most jurisdictions charge a valuation-based fee of about 0.5–2% of project value, plus plan review and per-trade permit minimums.

How long does a ADU or garage conversion permit take in Seattle?

Simple trade permits are often issued over the counter in Seattle. Where plan review applies, WA turnaround typically runs 3–6 weeks. Submit complete drawings the first time — resubmittals are the most common cause of delay.

Who pulls the permit — me or my contractor?

Usually your contractor pulls permits for a ADU or garage conversion, and their license is attached to the work. A contractor who asks you to pull an owner's permit for contractor-performed work is shifting liability onto you — treat that as a red flag when reviewing bids.

More Seattle permit guides

ADU / Garage Conversion permits in other WA metros

Is your ADU or garage conversion bid fair?

A typical Seattle ADU or garage conversion runs $214,448. Check your contractor's bid — permits included — against live 2026 local data, free.

Seattle ADU or garage conversion costs AUDIT MY BID

Data sources: Zonda Cost vs Value 2025; Houzz 2024 Cost Guides; BLS OEWS 2023; FRED regional price indices; Reddit homeowner & contractor reports.

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ADU / Garage Conversion Permits in Seattle, WA