Deck Building Code in Ontario: What Your Permit and Inspections Cover

The Ontario deck code asks for footings below frost depth, guards on any deck more than 600 mm above grade, stairs with set rise and run, and a ledger fastened and flashed to the house. Kitchener, Waterloo and Guelph require a building permit once a deck is about 24 inches (600 mm) above grade, and Kitchener and Waterloo also when it is roofed. Your municipality's building department confirms the details.

What the Ontario deck code covers

There is no stand-alone deck code. Deck rules come from the Ontario Building Code, mostly the Part 9 rules for houses and small buildings, and from your city's permit process. The current Building Code is O. Reg. 163/24. It adopts the National Building Code of Canada 2020 as amended by Ontario and took over from the earlier code at the start of 2025.

For the question people search as the Ontario deck building code PDF: the province does not publish one deck guide. Cities fill the gap with handouts, drawing checklists and standard details, so ask your building department for its deck package. Here is the short version:

Treat this table as a guide, not a substitute for your city's drawing checklist.

Do decks need a building permit in Ontario?

Often, yes, and the city decides. These are the city pages for our area:

• Kitchener: a permit for a deck or porch 24 inches or more above the ground at any point, or covered by a permanent roof.
• Waterloo: a permit for a deck more than 2 feet above ground, or one with a roof or cover.
• Guelph: a permit when any part of the walking surface is 24 inches or higher above finished grade.
• Cambridge: its permit page does not name decks, so call the building division before you plan.

A deck under the height trigger may not need a building permit, but zoning rules such as setbacks still apply, and Waterloo says so directly.

Replacing an existing deck. Guelph lists structural changes to an existing deck, and replacing guards, among the jobs that need a permit. A rebuild of the frame, footings, stairs or guards on a raised deck is the safe case to treat as permit work. Swapping worn boards on a sound frame is less clear. Ask your building department whether it counts as repair. Our guide to building permits for exterior renovations covers other jobs.

Footings below the frost line

Freeze-thaw cycles push shallow footings up and down, which can tilt a deck and pull stairs away from it. Footings go below the frost line, which is typically about 1.2 m (4 feet) in this region. Helical piles are an alternative to poured footings.

Footing size depends on the load and the span, so cities publish span tables. Kitchener posts standard details with span tables, and Waterloo asks for footing size and depth on the side-view drawing. Waterloo also lists a footing inspection before the concrete is poured. Plan for it, because it is hard to inspect footings after they are buried.

Frost depth is also the reason to call Ontario One Call before you dig. It is a free locate service for buried utilities.

Deck guard height and railing rules

A guard (the code word for a railing) is required when the deck surface is more than 600 mm (about 24 inches) above the ground. Under the Ontario rules:

• Height: at least 900 mm (about 36 inches), or 1070 mm (about 42 inches) when the deck is more than 1.8 m above the ground.
• Openings: the gaps between pickets, balusters or cables must be small enough that a sphere 100 mm (about 4 inches) across cannot pass.
• Strength: guards must carry the loads the Code specifies, so posts and their connections matter as much as the pickets.

Material matters at permit time. Kitchener keeps an approved list of guard and composite decking products, and a system not on the list needs supporting evidence such as an engineering or testing report. Ask the city for its list before you pick a railing.

Guards are the most common thing owners change late in a project. Confirm the height and the opening size on your drawings first. For a more detailed look at railing materials, see our deck railing installation guide.

Ontario deck stair code: rise, run and handrails

Stairs on a deck are treated as private stairs, which includes exterior stairs that serve a house. The numbers below come from Table 9.8.4.1 of the Building Code, as amended for stairs on January 1, 2022 (O. Reg. 88/19).

Older plans and online calculators may show a smaller minimum run, so check the date on anything you rely on. Handrails and landings follow their own rules. The number of risers that triggers a handrail, the side it goes on and its height are set out in Part 9, and your building department confirms them for your layout. Stair details are a common reason a drawing comes back for changes.

Ledger board, drawings and inspections

An attached deck fastens to the house with a flashed ledger board. Flashing keeps water out of the wall and the ledger, because a rotted ledger is a serious failure. A freestanding deck carries its own beams and posts and does not rely on the house. Either type must be designed and shown on drawings.

For a permit, expect to supply:

• A site plan with the deck, its size and the distance to each property line.
• A plan view showing posts, beams, joists, stairs and decking.
• A side view showing the deck height, the guard height and the footing size and depth.
• Detail drawings for the ledger connection, guard attachment and stairs.

Waterloo lists three inspections: footings, framing and the final. Other cities set their own stages, so ask when to call. Zoning is separate from the Building Code. Guelph points owners to its Zoning Services for setback questions, so check distances to the property line and any easement before you design.

Before you build or replace a deck

1. Measure the height of the deck surface above grade at its highest point.
2. Call your building department and ask whether a permit is needed. Mention the project clearly: new, rebuild, boards only, or new guards.
3. Ask for the city's deck handout, drawing checklist and any approved railing list.
4. Check zoning setbacks and any easements on your survey.
5. Book locates through Ontario One Call before digging.
6. Get a written estimate that names the footings, framing, ledger flashing, stairs and guards.

D&D Exterior Finishing builds decks in pressure-treated wood, cedar, composite and aluminum, with railings and stairs. Our free written estimate notes whether a permit is likely needed, and your municipality confirms. See the deck building service page and our guide to choosing a deck builder.

Deck code questions homeowners ask

Do you need a permit to replace an existing deck?

It depends on the work and the city. Guelph requires a permit for structural changes to a raised deck and for replacing guards. A rebuild of the frame, footings or stairs on a deck 24 inches or higher should be treated as permit work. Ask your building department whether a boards-only swap counts as repair.

Do decks need permits if they are low to the ground?

Often not. Kitchener, Waterloo and Guelph set the building permit trigger at about 24 inches (600 mm) above grade, and Kitchener and Waterloo also count a roof. A low deck still has to follow zoning rules such as setbacks. Cambridge does not name decks on its permit page, so confirm with its building division.

How deep do deck footings need to be in Ontario?

Footings go below the frost line so frost cannot lift them. In this region that is typically about 1.2 m (4 feet). Helical piles are an alternative to poured footings. Waterloo inspects footings before the concrete is poured, so do not cover them up before the inspector has seen them.

How high does a deck railing need to be in Ontario?

A guard is required when the deck is more than 600 mm above the ground. It must be at least 900 mm (about 36 inches) high, or 1070 mm (about 42 inches) when the deck is more than 1.8 m high. Openings must stop a 100 mm ball. Confirm details with your building department.

Devon Moore, Operations Lead Co-Founder & Operations Lead — D&D Exterior Finishing

Devon Moore is the co-founder and Operations Lead at D&D Exterior Finishing, specializing in siding, roofing, windows, and exterior renovations across Waterloo Region.