Do I need a permit to build a 10x10 shed in Ontario?

No. A 10x10 shed is 100 square feet (about 9.3 m²), which is well under the 15 m² (~161 sq ft) Ontario Building Code exemption. As long as it has no plumbing, no hard-wired electrical, meets your township's setbacks, and isn't in a regulated area like a shoreline or heritage district, you do not need a building permit.

How big can a shed be in Ontario without a permit?

Under the Ontario Building Code, a shed up to 15 square metres (about 161 sq ft) is exempt from a building permit, as long as it is one storey, has no plumbing, has no permanent electrical, and meets all township setback and zoning rules. Sizes like 10x16, 12x12, and 11x14 qualify; a 12x14 (168 sq ft) does not.

Does my shed need a permit in Cobourg or Port Hope?

Cobourg and Port Hope both follow the Ontario Building Code 15 m² exemption. However, both have Heritage Conservation Districts where even small sheds may require a Heritage Permit. Lakefront and shoreline properties may also need approval from the Ganaraska Region or Lower Trent Conservation Authority. Verify with the municipal building department before you start.

Do I need a permit for a shed with electricity in Ontario?

Yes. Any hard-wired electrical — outlets, lights, sub-panels wired to your home's breaker — triggers a building permit and a separate Electrical Safety Authority (ESA) inspection in Ontario. A plug-in extension cord run from the house is not regulated, but is not a safe long-term solution.

What is the setback for a shed in Northumberland County?

Most Northumberland County townships require sheds to be set back 0.6 m to 1.2 m from side and rear lot lines, with larger setbacks from a front lot line. Shoreline properties on Rice Lake, Lake Ontario, or the Trent River have additional Conservation Authority setbacks. Always check with your specific township office before building near a property line.

Do You Need a Building Permit for a Shed in Ontario? (The 15 m² Rule — Plus What Cobourg, Port Hope, and Hamilton Township Actually Enforce)

If you’re planning to build a shed in Ontario this year, the first question is almost never “what should it look like.” It’s “do I need a permit?” — and the answer Google gives you usually starts with “it depends.”

Here’s the actually-useful version, from a builder who pulls these permits for a living.

The short answer

In most of Ontario, you do not need a building permit for a shed if all of the following are true:

The shed is under 15 square metres (roughly 161 sq ft — that’s a 10×16, a 12×12, or an 11×14).
It is one storey.
It has no plumbing.
It has no permanent electrical (a plug-in extension cord is fine; a hard-wired circuit is not).
It meets your township’s setback and zoning rules.

Cross any one of those lines — even by a hair — and you’re back in permit territory. A 12×14 shed (168 sq ft) needs a permit. A 12×12 shed with a baseboard heater hard-wired in needs a permit. A 10×10 shed three feet from your property line might need a zoning variance, which is its own paperwork.

Where the 15 m² rule actually comes from

The number lives in the Ontario Building Code (OBC), Division A, Part 1 — buildings “exempt from the requirement to obtain a permit.” It applies province-wide, which is why you see “15 sq m” repeated on every Ontario township’s website.

What people miss is that the OBC sets the ceiling, not the floor. Your township can layer additional rules on top:

Some require a permit at smaller sizes if the shed is in a regulated area (shoreline, ravine, environmentally protected land).
Some have minimum lot-coverage rules that count every outbuilding on your property toward a total.
Most have setbacks of 0.6 m to 1.2 m from side and rear lot lines for a shed.

What Cobourg, Port Hope, and the surrounding townships actually do

We pull permits across Northumberland County most weeks. Here’s what we see on the ground (verify with your township before you start — these rules change, and we’re builders, not lawyers):

Town of Cobourg. Follows the 15 m² OBC exemption. Side and rear setback typically 0.6 m. Heritage districts have extra design review — if you’re in the Heritage Conservation District, even a small shed may need a Heritage Permit on top of (or instead of) a building permit.

Municipality of Port Hope. Follows OBC. Heritage Conservation Districts apply in downtown Port Hope; outside those, a shed under 15 m² with proper setbacks is permit-exempt.

Hamilton Township. (This is the township that surrounds Cobourg — Bewdley, Bailieboro, Gores Landing, Camborne.) 15 m² exemption applies. Lakefront properties on Rice Lake have additional shoreline setbacks under the Conservation Authority — you’ll usually need approval from Ganaraska Region Conservation Authority before you build anywhere near the water.

Cramahe Township. (Castleton, Colborne.) 15 m² exemption. Watch the agricultural zone rules — an “accessory building” on a rural property has different size allowances than the same shed on a residential lot.

Alnwick/Haldimand Township. (Grafton, Roseneath, Centreton.) 15 m² exemption. If your property is over the Oak Ridges Moraine, you may have additional Conservation Authority review.

Trent Hills. (Campbellford, Hastings, Warkworth.) 15 m² exemption. Same shoreline note — Lower Trent Conservation has jurisdiction over much of the township.

Brighton. (Brighton, Codrington.) 15 m² exemption. Lakefront on Lake Ontario again triggers Conservation Authority review.

For any of the above, the township office can tell you in a 5-minute phone call whether your specific build needs a permit. The website rarely tells the whole story — the staff do.

When a permit IS needed (the four lines you cross most often)

You go over 15 m². A 12×14 shed is 168 sq ft (15.6 m²). Yes, those 7 sq ft over the line matter.
You add plumbing. Any pipe, even a hose bibb hard-plumbed in, triggers a permit.
You hard-wire electrical. Outlets, a sub-panel, lights wired to your home’s breaker — permit. Extension cord from the house — no permit.
It’s habitable. The minute you put insulation, a heat source, and any living-use intent in a shed, you’ve built an “accessory dwelling unit” — and that’s a much bigger conversation involving zoning, septic, and sometimes a minor variance.

The hidden 5th line: lot coverage

Even if your shed is under 15 m² and permit-exempt, your township still cares about lot coverage — the total footprint of all buildings on the lot. Most rural-residential lots cap accessory buildings at 5–10% of the lot, depending on zone. If you already have a detached garage, a workshop, and a bunkie, your next shed might push you over — and that triggers a zoning compliance issue even without a building permit.

What we tell customers

Three honest answers we give every week:

If you’re under 15 m², no plumbing, no hard-wiring, and you have lots of room around your lot lines: build it. You don’t need a permit. Just keep it inside the setbacks and don’t put it on top of a septic bed.

If you’re anywhere close to the line on size, setbacks, or electrical: call the township. A 5-minute phone call to your building department saves you a $2,000 fix later when an inspector spots it from the road.

If you want anything heated, insulated, or wired: plan for a permit. The permit itself usually runs $200–$600 in Northumberland County, and the inspection process is straightforward. It’s not the obstacle most people fear it is.

When in doubt, ask before you frame

The single most expensive shed mistake we see isn’t going one foot over 15 m². It’s framing the whole thing and then finding out you’re 0.3 m inside a setback, or sitting on top of a septic field, or in a regulated wetland buffer. Those builds get torn down, not retroactively approved.

Five-minute phone call. Then build with confidence.

Need a shed built right the first time?

We build custom storage sheds, backyard workshops, and outbuildings across Northumberland County and rural Ontario — permit-pulled when needed, code-built always. Get a free estimate or call 905-797-3000.