Do you need a permit to build a deck in the GTA?
A deck over 600 mm above grade needs guards under the Ontario Building Code and a building permit in most GTA municipalities. Here are the thresholds, guard heights and permit authorities, city by city.
Key takeaways
- A deck is a building permit question and a fence is a by-law question. Different departments, different forms, different timelines.
- 600 mm above grade is the threshold that decides most of it. Below it, the Ontario Building Code asks for no guard. Above it, you need guards and, in most GTA municipalities, a permit.
- Guard height under the Code is 900 mm where the walking surface sits 600 to 1,800 mm above grade, and 1,070 mm once it passes 1,800 mm.
- Footings go below the 1,200 mm frost line everywhere in this market, so depth is not something a municipality negotiates.
- An Ontario One Call locate is required by law before anyone digs, with a five business day minimum on a single property.
Two homeowners on the same street can get different answers about whether their deck needs a permit, and both answers can be correct. The height of the finished walking surface above the ground is what separates them. This guide covers the thresholds that apply across the Greater Toronto Area, the guard dimensions an inspector measures with a tape, and which office issues the permit in each city we work in.
When a deck permit is required in Ontario
Decks are governed by the Ontario Building Code, enforced by the building department of your own municipality. Fences are a separate instrument: a municipal fence by-law, enforced by by-law services. That split explains why a fence contractor can start next week and a deck build has a lead time in front of it.
The Code's structural trigger is height above grade. Once a deck's walking surface is more than 600 mm above the ground, the structure requires a guard under Ontario Building Code section 9.8.8. Below that height, no guard is required by the Code at all, which is why a ground level platform is a genuinely simpler project than a deck off a raised main floor.
Permit triggers track the same number in most of the region. Whitby states it plainly: decks over 600 mm require a building permit, and Zoning By-law 1784 applies to the deck regardless of its height. That second half is the part people miss. A low platform can be exempt from a permit and still be subject to setbacks and lot coverage limits under zoning.
If you are planning a new deck build, the honest sequence is to settle the height first, because it determines the permit, the guards and a meaningful part of the price.
The 600 mm rule, translated
Metric is what the Code is written in and imperial is what gets spoken on site. These are the four numbers worth memorising.
| Code dimension | Imperial equivalent | What it governs |
|---|---|---|
| 600 mm | about 24 in | Guards become mandatory above this height |
| 900 mm | about 36 in | Guard height for surfaces 600 to 1,800 mm above grade |
| 1,070 mm | about 42 in | Guard height for surfaces above 1,800 mm |
| 1,800 mm | about 6 ft | The height at which the taller guard takes over |
Source for the guard dimensions: Ontario Building Code section 9.8.8, as summarised in the OBC 2024 deck railing guides published by misterbaluster.com and deckmaster.ca, and in the OBC text at buildingcode.online.
Guard and railing heights an inspector measures
A guard that is the right height can still fail on its openings. Under the Code, no opening in a guard may pass a 100 mm sphere. That single rule is what sets baluster spacing, and it is the most common reason a finished railing gets rejected on a first inspection.
Stairs carry their own dimension. A handrail sits 865 to 965 mm above the stair nosing, measured on the slope rather than off the tread. If your build includes deck stairs, the handrail height and the guard height are two separate measurements and they are frequently confused for one.
Oakville publishes the same set of thresholds in its own deck guidance: guards required above 60 cm, minimum guard height 1.07 m, openings no greater than 100 mm. Oakville also enforces non-compliance through its Administrative Penalty By-law, which is a ticket rather than a conversation, and heritage designated properties there need additional approval before a permit is issued.
Permit authority by GTA municipality
The permit is always issued locally, never regionally. Durham Region confirms on its own permits page that permits are a lower tier matter, so the city or town is the right phone call.
| City | Permit authority | Documented local detail |
|---|---|---|
| Toronto | Toronto Building | Fence on an attached uncovered deck is measured from the deck surface, to a maximum of 2 m, per City of Toronto 311 article kA06g000001cvVtCAI |
| Whitby | Whitby Building Services | Decks over 600 mm require a permit; Zoning By-law 1784 applies at any height |
| Oakville | Oakville Building Services | Guards above 60 cm, minimum 1.07 m, openings under 100 mm; heritage properties need extra approval |
| Pickering | Pickering Building Services | The City publishes a Deck Construction Guide listing the drawings and approvals required |
For the rest of the region, the building department carries the municipality's name: Mississauga Building Division, Brampton Building Division, Markham Building Standards, Vaughan Building Standards, Hamilton Building Division, Richmond Hill Building Services, Milton Building Services and so on. Each city service area page names the authority and the local rule that makes that municipality different from its neighbour.
Footings, frost depth and the locate you cannot skip
Footing depth is the one specification that does not change across this market. The frost line is 1,200 mm throughout the GTA, and deck piers are set below it. A footing that stops short will heave in the first hard winter and take the ledger, the guards and the stair stringers out of alignment with it.
Before any of that digging happens, the locate has to be filed. Ontario One Call is a legal requirement, not a courtesy, and the HCRA names building a fence or a deck explicitly as work that triggers it. Landscape Ontario records the timelines:
- Five business days minimum for a locate on a single property.
- Ten business days where the project spans multiple properties, or sits on land with no civic address.
- Only after the locate clears does excavation for piers or posts begin.
This is why a deposit books an assessment rather than a start date, and why a written final price follows a site visit instead of preceding it.
What to have ready before you apply
Building departments across the region ask for broadly the same package. Pickering's Deck Construction Guide is the clearest published example of what that package contains.
- A site plan showing the deck's position, its setbacks from every lot line, and lot coverage.
- A framing plan with joist size, joist spacing and beam spans.
- A footing detail showing pier diameter and depth below the 1,200 mm frost line.
- A guard and stair detail carrying the guard height, the baluster opening and the handrail height.
- Confirmation of the Ontario One Call locate reference.
Zoning is worth checking before the drawings are finished rather than after. Setbacks and lot coverage decide how big the deck can be, and there is no version of that conversation where a permit reviewer moves the lot line.
If you want the structure priced before you commit to a drawing set, get an online estimate and the crew confirms the measured price on site. Where guards are in scope, the deck railing page covers the options that satisfy the 900 mm and 1,070 mm heights without looking like code compliance.
Questions we get asked
01How high can a deck be before it needs a permit in Ontario?
The threshold used across the GTA is 600 mm (about 24 in) above grade. Whitby states it directly: decks over 600 mm require a building permit. Below that height the Ontario Building Code requires no guard, but zoning still applies. Whitby's Zoning By-law 1784 governs the deck at any height, which means setbacks and lot coverage apply even to a permit-exempt platform.
02What is the legal railing height for a deck in Ontario?
Under Ontario Building Code section 9.8.8, a guard is 900 mm high where the walking surface is 600 to 1,800 mm above grade, and 1,070 mm where it exceeds 1,800 mm. No opening in the guard may pass a 100 mm sphere. A stair handrail sits 865 to 965 mm above the stair nosing, measured on the slope.
03How deep do deck footings need to be in the GTA?
Below the frost line, which is 1,200 mm across every municipality in this market. That depth does not vary by city. A footing that stops short of it will heave in the first hard winter and pull the ledger, guards and stair stringers out of alignment.
04Do I need a locate before digging deck footings?
Yes. Ontario One Call locates are required by law in Ontario before digging, and the HCRA names building a deck or a fence explicitly. Allow a minimum of five business days for a single property, or ten business days where the work spans multiple properties or land with no civic address.
