Do You Need a Permit to Replace Siding or Windows? County by County
Short version: swapping siding or windows like-for-like — same openings, same sizes, nothing structural — is often exempt from permits or covered by a simple one, while changing opening sizes, repairing structure, or working on shoreline, critical-area, or historic properties needs a permit everywhere. The rules belong to whoever governs your address: your city inside city limits, your county outside them. One phone call to that office settles it, and on permitted work the contractor — not you — should carry the permit and inspections in the bid.
The line that actually decides it: like-for-like vs. changing the building
Permit rules vary by jurisdiction, but they all draw roughly the same line. On one side is like-for-like replacement — new siding or new windows going into the same openings, same sizes, no structural changes. Many jurisdictions treat some or all of this as exempt from a building permit, or handle it with a simple over-the-counter one. On the other side is work that changes the building, and that side is permitted essentially everywhere:
- Changing an opening. Enlarging a window, shrinking one, adding one, or turning a window into a door means cutting framing and re-establishing headers — that's structural work.
- Structural repair behind the siding. If tear-off reveals rotted sheathing or framing that needs replacement, the repair itself typically triggers permit requirements even when the siding swap alone wouldn't have.
- Egress and safety glazing. Bedroom windows have minimum escape-opening requirements, and windows near doors, floors, tubs, and stairs need tempered glass. Replacements are expected to meet current requirements, not just match what was there.
- Energy code. Washington's state energy code applies to replacement windows — new units have to meet the current maximum U-factor requirements, which is one reason the single-pane era isn't coming back.
Two more layers can override everything above: where the house sits and what the house is. Shoreline areas, designated critical areas, and historic districts each add their own review, and they're common across Northwest Washington — especially near the water. When in doubt, the jurisdiction's answer is the only one that counts.
The single most useful pre-project phone call isn't to a contractor — it's to your own building department. Tell them your address and the exact scope, and ask what they require. It takes ten minutes, it's free, and every bid you collect afterward can be checked against what they told you.
County by county: who you actually ask
The most useful thing to know isn't a rule — it's who has jurisdiction over your address. In Washington, if your home is inside city limits, the city's building department issues your permits. If it's in an unincorporated area, the county's building or community development department does. That single fact sorts out most of the confusion, because neighbors a mile apart can answer to different offices with different thresholds.
- Whatcom County. Inside Bellingham, Ferndale, Lynden, Blaine, and the other incorporated cities, ask that city's building department. Unincorporated addresses — Birch Bay, Custer, Acme, and a large share of the county — go through Whatcom County's permitting office.
- Skagit County. Mount Vernon, Burlington, Anacortes, and Sedro-Woolley each run their own permitting; unincorporated Skagit addresses go through the county. Waterfront properties around Anacortes and the bays should expect shoreline questions.
- Snohomish County. The most fragmented of the five — many incorporated cities, each with its own building department, plus a very large unincorporated population served by the county. Verify which side of a city limit you're on before assuming anything.
- Island County. Oak Harbor and Coupeville handle their own; the rest of Whidbey and Camano goes through the county. Lots of shoreline here, so waterfront replacements deserve an early phone call.
- San Juan County. Essentially the whole county — Friday Harbor is the only incorporated town — runs through county permitting, and shoreline rules touch a large fraction of island properties.
Every one of these offices answers permit-threshold questions by phone or email, usually the same day. Describe the exact scope — "replacing siding with the same profile, no sheathing work" reads very differently to a permit tech than "re-siding the house."
What this means for your project (and your bid)
First: the permit is not your problem to carry. On permitted work, the contractor should handle the application, post the permit, and schedule the inspections as part of the job — it should appear in the bid as a line item, not a surprise. Be wary of any contractor who suggests skipping a permit the jurisdiction requires, or who wants the permit pulled in your name as an owner-builder while they do the work. That move shifts liability for code compliance onto you and often signals a registration problem on their end.
Second, inspections are a feature, not a tax. On a window project, the details that matter — openings measured individually, flashing integrated with the weather barrier, sill pans where the assembly calls for them — mostly disappear behind trim by the end of the job. An inspection is one more set of eyes on that work while it can still be seen, at exactly the stage where shortcuts hide.
Third, unpermitted work doesn't stay free. It surfaces at sale time, when a buyer's inspector or lender asks for permit history and the answer becomes a negotiation against you; it can complicate insurance claims; and retroactive permits generally cost more time and money than doing it right the first time. If part of our scope needs a permit, we say so in the bid, we price it, and we handle it — and if you're not sure whether a past project on your house was permitted, your jurisdiction's permit history for the address is public and worth pulling before you sell.
