Decks and fences are some of the most common home upgrades because they feel straightforward: build a platform, add steps, add a fence for privacy. The problem is that many “simple” projects become regulated based on height, location, and structure. That’s why homeowners sometimes get a stop-work notice even when the project looks similar to something they’ve seen in the neighborhood.
This guide focuses on the practical permit triggers that most people miss—especially in Seattle’s older neighborhoods where slopes, retaining walls, and tight property lines are common.
1) Deck permits usually come down to height and structure
The fastest way a deck triggers permits is when it sits high above grade. Homeowners often measure from the top of the deck down to the lowest spot in the yard and underestimate how the city measures it. On sloped lots, a deck can be low on one end and “tall” on the other.
- Over a threshold height: Taller decks typically trigger guardrail requirements and structural review.
- Attached to the house: Connection points, ledger boards, and load paths become safety concerns.
- Supporting a roof/pergola: Once you add a structure above, wind and load requirements increase.
2) Stairs and guardrails are common “scope creep” triggers
A deck can start as a platform and later get stairs, landings, and guardrails. Each addition matters because it changes safety requirements. Guardrails have strict spacing and height rules, and stairs have rules for rise/run geometry, handrails, and landing sizes.
- Adding stairs: Can trigger requirements for handrails, landings, and safe egress paths.
- Adding guardrails: Brings spacing and height rules that must be built correctly to pass inspection.
- Changing existing stairs: “Replacing” isn’t always treated as “repair” if geometry changes.
3) Fences aren’t always “no permit,” especially for height and visibility
Fences are usually simpler than decks, but permit triggers show up when you change height, add a solid privacy barrier, or build near areas where visibility matters (driveways, intersections, and corner lots). The city cares about sightlines: drivers leaving a driveway should be able to see oncoming traffic.
- Height limits: Front yards often have lower allowable heights than side/back yards.
- Corner lots: Visibility triangles can restrict where tall fencing can go.
- Gates and openings: Can still be an issue if overall sightlines are blocked.
4) Retaining walls change everything (even if you “only want a fence”)
In Seattle, many yards rely on retaining walls because of grade changes. If your fence sits on top of a retaining wall, or you plan to modify a wall to support a fence, the project may be treated as retaining wall work rather than just “fencing.” Retaining walls can require engineering, drainage considerations, and permit review sooner than people expect.
5) Property lines and neighbor conflicts are a hidden risk
A lot of deck and fence headaches aren’t code issues—they’re property line issues. Homeowners build “where they think the line is,” and only discover the problem when a neighbor disputes it. On narrow lots, being off by even a foot can create major disputes and costly rework.
- Assumed boundary ≠ legal boundary: Old fences aren’t always on the true line.
- Encroachment risk: A deck footing over the line is much harder to undo than a fence panel.
- Setbacks: Even if the line is correct, setbacks may restrict placement.
Pre-check list: 10 minutes that can save weeks
Before you buy lumber, answer these questions:
- What is the deck height at the highest point above grade?
- Will you add stairs, landings, or guardrails (now or later)?
- Is the deck attached to the house, or free-standing?
- Is the fence in a front yard or near a driveway/corner where visibility matters?
- Is any part of the fence/deck interacting with a retaining wall or slope?
- Are you confident about the property line location?
Want clarity before you build?
Use the Seattle Permits report to spot deck/fence permit triggers and avoid mid-project surprises.