What Does a Custom Shed Cost in Snohomish & King County? (2026 Guide)

If you’ve started pricing out a custom shed builder in Snohomish County for your property, you’ve probably noticed the numbers online are all over the map — a box-store kit for a few hundred dollars sitting next to a “custom shed” quote in the tens of thousands. Both are real, and the gap between them comes down almost entirely to one thing: whether you’re buying a prefab box or having something built for your lot. Here’s what actually drives the number.

Custom Shed Cost Per Square Foot

Nationally, a custom-built shed — site-built to your specs rather than assembled from a kit — typically runs $45 to $100 per square foot, with some fully custom builds (finished interiors, higher-end siding, larger footprints) landing north of that. A prefab or kit shed, by comparison, usually falls in the $10–$40 per square foot range. That difference isn’t padding — a custom build is framed and finished on-site to fit your yard, your grade, and how you actually plan to use the space, where a kit is a standard box regardless of what’s around it.

Put in dollar terms, a 10×12 custom shed (120 sq ft) lands roughly in the $5,400 to $12,000 range before options; a 12×20 (240 sq ft) shop-style shed runs closer to $10,800 to $24,000. Where you fall in that range depends on the factors below.

What Actually Drives the Price

A handful of choices move the number more than square footage alone:

• Foundation — stacked blocks are the cheapest option, a gravel pad is a step up, and a poured concrete slab costs the most but holds up best under a heavier shed or a workshop full of equipment.
• Siding and roofing — wood siding, vinyl, and metal all price differently, and a shingled roof costs more than a simple metal one.
• Windows and doors — every window, and the difference between a single door and a double barn door, adds to the total.
• Electrical — running power to a shed (outlets, lighting, a breaker sub-panel for a workshop) is one of the bigger optional line items.
• Size and layout — a simple rectangular storage shed costs less per square foot than one with a loft, a covered porch, or an unusual footprint.

Custom vs. Kit vs. DIY

It’s worth being honest about the alternative: a DIY kit shed can run as little as $1,500–$4,000 in materials for a basic 10×10, and that’s a legitimate option if you’re comfortable with the build yourself and don’t need it to match your house or hold up to Western Washington winters for the next 30 years. A custom-built shed costs more because you’re paying for site-specific framing, a foundation matched to your soil and drainage, and finish work that’s built to last — not a mail-order box.

Permits — Read This Before You Budget

Cost and permitting are connected more than most homeowners expect. In unincorporated Snohomish County, a single-story storage shed is exempt from a building permit at 200 sq ft or smaller inside an Urban Growth Area (400 sq ft outside one) — but a permit-exempt shed still can’t have a heating system, and it still has to meet setback rules. We wrote up the full breakdown, including the garage and larger-building numbers, in our guide to Snohomish County shed permits. Worth a read before you lock in a size, since crossing that 200 sq ft line can add permit fees and timeline to your project.

Shed or ADU? A Quick Gut-Check

If the wish list has grown to include a bathroom, a kitchenette, or a place someone could actually sleep overnight, you’re not pricing a shed anymore — you’re pricing an accessory dwelling unit, and the cost and permit math both change substantially. A storage shed and an ADU get regulated very differently in both Snohomish and King County, so it’s worth sorting out which one you’re actually building before you get too far into budgeting either.

Why a Real Quote Beats a Blog Post

Every number above is a market range, not a quote — the only way to know what your shed actually costs is a site visit. Your lot’s access, grade, soil, and how far the build site sits from a power source all move the price, sometimes more than the size of the shed itself. If you’re also weighing a larger structure, the same site factors apply to a detached garage or carport build — worth a look if storage is really the goal and a shed might come up short.

We build custom sheds on-site across Snohomish and King County, sized and finished for how you’ll actually use the space. Get in touch with our team for a real number on your property, not a national average.

Sources: cost-per-square-foot ranges are 2026 market data compiled from Angi, HomeGuide, and Lawn Love shed-cost guides, not NW Structures pricing. Permit figures per Snohomish County Planning & Development Services.