Building a Backyard Deck or Shed in Ontario: When You Need a Permit and the Zoning Rules That Apply Anyway

The permit is the question everyone asks first, and the one that is easiest to answer last. Where the structure sits, how big and tall it is, and whether it is attached, plumbed or roofed decide most of the answer before anyone looks at a permit form.

I’m Arthur Zhao, a Toronto real estate Broker. A family that has just moved in usually has its first summer list drafted before the boxes are gone: a shed for the mower and the bikes, and a deck off the back door so the kitchen opens onto something better than a step and a patch of grass. Both feel like weekend projects. Both are also things the city has rules about, and those rules are not only about permits.

The permit is what everyone asks about first, but it is easier to answer last. Start with where the structure sits on the lot, then how big and tall it is, then whether it is attached, plumbed or roofed. Only after that does the permit question have a clean answer. This article walks through it in that order, using the 2024 Ontario Building Code and the City of Toronto’s zoning by-law as the worked example. If you live outside Toronto, your city has its own by-law and its own permit page, and the numbers may differ.

1. Where on the lot

Toronto’s rules for sheds, detached decks and similar structures sit in Article 10.5.60 of Zoning By-law 569-2013, which governs ancillary buildings or structures in the Residential Zone category. The clause numbers below come from the City’s Chapter 10 office consolidation (version date July 31, 2024, including city-wide amendments up to April 30, 2026). Other Ontario municipalities have their own zoning by-laws with their own numbers.

The front yard is off the table

The first location rule is short: “An ancillary building or structure in the Residential Zone category may not be located in a front yard” (10.5.60.10(1)). It does not depend on size, and it does not depend on whether a building permit is needed. A shed small enough to skip the permit is still a shed in a front yard.

Setbacks from the rear and side lot lines

Rear lot line. In ordinary cases, the minimum rear yard setback for an ancillary building or structure is 0.3 metres (10.5.60.20(2)(C)). Two situations change that: on a through lot where the neighbour’s house fronts the street behind you, the setback matches that house’s required front yard setback (10.5.60.20(2)(A)); and on a lot deeper than 45 metres, a structure taller than 2.5 metres or larger than 10 m² in floor area must be set back half its height (10.5.60.20(2)(B)).

Side lot lines. A structure in a side yard uses the house’s own required side yard setback (10.5.60.20(3)(A)). In the rear yard, it depends on distance from the house: less than 1.8 metres from the house, it uses the house’s side setback (10.5.60.20(3)(B)); 1.8 metres or more away, a separate set of rules applies (10.5.60.20(3)(C)), which is worth reading for your own lot type.

Distance from the house

An ancillary building or structure taller than 2.5 metres, or with a gross floor area greater than 10 m², “must be at least 1.8 metres from a residential building on the same lot” (10.5.60.30(1)). That 1.8-metre distance also changes the height and size limits in the next part, so measure it before you choose a kit.

Decks follow different location rules depending on whether they touch the house. A deck attached to or within 0.3 metres of a building must comply with the zone’s required minimum building setbacks (10.5.40.50(2)), with limited encroachments allowed: in a rear yard, a platform no higher than the first storey may encroach the lesser of 2.5 metres or 50% of the required rear yard setback, subject to a side-lot-line distance (10.5.40.60(1)(C)). A freestanding deck that is at least 50% open on its sides and sits no closer than 0.3 metres to the house needs rear and side setbacks equal to the greater of 0.3 metres or the height of its floor above the ground below (10.5.60.20(11)).

2. How big and how tall

Once the spot works, the by-law limits the structure itself. These caps apply to the shed you buy and to everything else ancillary on the lot.

Height and storeys

Maximum height is 2.5 metres if the structure is less than 1.8 metres from the house, and 4.0 metres in all other cases (10.5.60.40(2)). Height is measured from average grade to the highest point (10.5.60.40(1)). Whatever the height, an ancillary building or structure “may not have more than one storey” (10.5.60.40(3)).

For decks attached to a house, the floor of a platform at or below the first storey of a house (other than an apartment building) may be no higher than 1.2 metres above the ground at any point below it, with exceptions where the platform is attached to or within 0.3 metres of certain walls (10.5.40.50(4)).

Floor area and lot coverage

• One structure close to the house: anything less than 1.8 metres from the house is capped at 10.0 m² of floor area (10.5.60.50(3)).
• All ancillary structures combined (pools excluded): no more than 60.0 m² on a lot with 12.0 metres of frontage or more, and 40.0 m² in all other cases (10.5.60.50(2)).
• Lot coverage: ancillary buildings and structures count toward lot coverage, and together may not cover more than 10 percent of the lot area (10.5.60.70(1)(A)–(B)). That 10% cap does not apply to a lot with a detached or semi-detached houseplex, or a house with a secondary suite, if overall coverage of all buildings and structures stays at or below 45% (10.5.60.70(1)(C)).

If the garage, an existing shed and the new one together already approach the total, the next shed may be the one the by-law does not allow, even if it is small.

3. Attached? Plumbing? Roof?

These three questions are where a small project quietly turns into a different category.

Plumbing. The Building Code Act, 1992 treats “a structure occupying an area of ten square metres or less that contains plumbing” as a building (s.1(1), clause (b)). Size stops protecting you once there is a sink or a drain. The Building Code’s shed exemption requires that the shed “has no plumbing,” and Toronto’s permit page says an accessory structure that “is attached to an existing building and/or has plumbing” needs a permit “regardless of its size.”

Attached. The Code’s exemption also requires the shed to be “not attached to a building or any other structure.” A lean-to built against the house or the garage is outside it.

Roof or cover. Toronto’s deck exemption is written for an uncovered deck. The same page lists “enclosing an existing deck, porch or patio of any size” as permit work, and lists decks, porches and solariums among additions to an existing building that need a permit. The page does not address pergolas, gazebos or covered decks directly.

One more definition is worth knowing: under s.1(1)(a) of the Act, a “building” includes a structure occupying more than 10 m² “consisting of a wall, roof and floor or any of them.” The words “or any of them” are how a structure with only a floor, such as a deck, can fall inside the Act.

4. Only now: does it need a permit?

The starting rule is s.8(1) of the Building Code Act: “No person shall construct or demolish a building or cause a building to be constructed or demolished unless a permit has been issued therefor by the chief building official.” The exemptions are narrow.

Shed. According to Ontario’s Building Code Compendium (2024), under the 2024 Building Code (O. Reg. 163/24), Division C, Sentence 1.3.1.1.(6), a shed is exempt from the permit requirement under s.8 of the Act, and from compliance with the Code, if it:

• is not more than 15 m² in gross area,
• is not more than one storey in building height,
• is not attached to a building or any other structure,
• is used only for storage purposes ancillary to a principal building on the lot, and
• does not have plumbing.

Toronto’s permit page also lists accessory structures such as garages, workshops, carports, pool houses and cabanas larger than 10 m² (107 sq ft) as needing a permit. If your “shed” is really a workshop, read that line too.

Deck. Toronto’s page says a permit is needed to “Construct a deck more than 60 centimetres (24 inches) above ground.” Its exemption for an uncovered deck applies, in the page’s own words, provided:

• “its finished deck level is not more than 60 cm (24 inches) above the adjacent finished grade; and/or”
• “it does not form part of an exit required under the building code; and”
• “complies with the Zoning Bylaw.”

The “and/or” is the City’s wording. I have quoted it rather than paraphrased it, because the conditions read differently depending on how it is taken. If your deck is close to the line or forms part of a path out of the house, put the question to Toronto Building before you build.

The provincial Building Code’s shed exemption vs. Toronto’s permit page

If it goes up without a permit

Building something that needed a permit without one is a contravention of s.8(1) of the Building Code Act, and the Act gives the city several tools.

Orders first

An inspector who finds a contravention of the Act or the Code “may make an order directing compliance” and may require it to be carried out immediately or within a set time (s.12(2)). If that order is not followed, the chief building official may order that all or part of the construction stop (s.14(1), a stop work order).

Then fines

Failing to comply with an order, or contravening the Act, is an offence (s.36(1)). According to the Building Code Act, 1992 (current consolidation, 2026), on conviction an individual faces a fine of not more than $50,000 for a first offence and $100,000 for a subsequent one (s.36(3)); for a corporation the maximums are $500,000 and $1,500,000 (s.36(4)). Failing to comply with a stop work order under s.14(1) adds a fine of up to $10,000 per day the offence continues after the compliance deadline (s.36(6)). These are maximums set by the statute, not typical outcomes.

A zoning contravention is a separate matter from the Building Code Act. A structure that is exempt from a permit can still breach the zoning by-law, and the by-law has its own enforcement route.

Outside Toronto

The Building Code and the Building Code Act apply across Ontario, so the shed exemption and the fines above are the same in every municipality. The zoning by-law and the city’s permit guidance are local. Mississauga, Markham, Ottawa and every other municipality have their own by-laws, with their own setbacks, heights and coverage limits, and their own answer on decks. The Toronto numbers in this article are a worked example, not a rule for your city. Your local building department is the office that can answer for your lot.

What to do, in order

Two short lists, one for the store and one for the phone call.