The Ontario Building Code requires a 36-inch (900 mm) deck railing when your deck sits between 24 inches (600 mm) and 5 feet 11 inches (1,800 mm) above the ground. Higher than that, you need 42 inches (1,070 mm).
Both numbers sound simple. Then you stand in a backyard that slopes toward the fence, and your answer changes from corner to corner. We have built decks around here for over 10 years, and watched plenty of Town inspectors put a tape on a guard.
Below you will find which height applies to your deck, how the measurement works, and what the Building Division wants on your drawings.
When Is a Deck Railing Required?
Under Subsection 9.8.8 of the Ontario Building Code, you need a guard wherever your deck edge drops more than 24 inches (600 mm).
The Drop, Not Average Grade
The code looks at the real drop from your deck to the ground under the edge, so an average off your site plan will not satisfy an inspector. Where your yard slopes, the deepest drop decides it.
One High Corner Sets the Rule
You have probably measured at the back door. If that reads 20 inches while your far corner reaches 28, the code follows the corner.
Under 24 Inches (600 mm), No Guard Needed
Below that height, the rules on guard height, spacing, and climbing fall away, and any guard you add by choice is exempt too. Joist depth and footing height decide whether you clear it, so the measurement that matters is at your lowest point. That is the thinking behind our expert ground-level deck installation.
Covering or Screening Changes Nothing
Installing privacy screens, lattice panels, or decorative deck skirting doesn’t reduce the measured drop or exempt your deck from the code.
If the deck edge is more than 24 inches (600 mm) above grade, a code-compliant guardrail is still required. The screen can be added for privacy, but it cannot serve as a substitute for a properly built safety guard.
Read More: How to Install Deck Railing: A Step-by-Step Guide for Ontario Homeowners
What Is the Minimum Deck Railing Height?
The required deck railing height depends on the distance between your finished deck surface and the finished ground level. Under the Ontario Building Code, the key threshold is 5 feet 11 inches (1,800 mm).
Decks 600 mm to 1800 mm Above Grade: 36 Inches
Most backyard decks in Newmarket sit here, where the Ontario Building Code requires a 36-inch (900 mm) guardrail. That height runs from your finished deck surface to the top of the finished rail. This is why builders set posts long and trim them after the boards go down; cutting sooner leaves you an inch and a half short.
Decks Over 1800 mm Above Grade: 42 Inches
If any part of your deck is more than 1,800 mm above grade, the required guardrail height increases to 42 inches (1,070 mm).
This is common on walkout properties in neighbourhoods like Stonehaven, Woodland Hill, and Glenway Estates, where the ground slopes away from the house and creates a much greater drop at the deck edge. Our professional elevated deck building in Newmarket starts with a tape on the ground.
Why Some Guides Say 42 Inches for Every Deck
Many Ontario guides simply recommend 42-inch guardrails for every deck because it’s the higher code requirement and avoids confusion. Although the Ontario Building Code allows a 36-inch (900 mm) guard on detached homes with a drop of 1,800 mm or less, that exception doesn’t always apply once part of the deck exceeds the threshold.
If your deck is close to 1,800 mm, building to 42 inches is often the safest way to remain compliant and avoid future modifications.
Read More: How to Clean Composite Decking
Minimum Railing Height by Deck Type
| Deck type | Required guard height |
| Ground-level deck under 24 inches (600 mm) | No guard required |
| Attached deck, 24 inches to 5 feet 11 inches | 36 inches (900 mm) |
| Raised deck over 5 feet 11 inches | 42 inches (1,070 mm) |
| Second-storey deck | 42 inches (1,070 mm) |
| Multi-level deck | Each level measured on its own |
| Pool deck | 36 or 42 inches, plus pool fence rules |
| Walkout deck | Usually 42 inches (1,070 mm) |
How to Measure Deck Railing Height Correctly
Guard height runs straight up from your finished deck surface to the top of the cap rail, while stair guards get measured against the tread nosing line.
Step 1: The finished deck surface is your starting point
Start your measurement from the top of the finished deck boards, not the joists or framing below. Since decking adds thickness to the finished surface, measuring too early can leave the completed guardrail below the minimum height required by the Ontario Building Code.
Step 2: Measure to the Top of the Guardrail
Measure straight up to the highest point of the finished cap rail, as this forms part of the overall guard height. Keep the tape measure perfectly vertical rather than following the angle of the post or railing to get an accurate code measurement.
Step 3: Use the Correct Reference for Stair Guards
Stair guards aren’t measured from an individual tread. Instead, the height is taken from an imaginary line connecting the front edges (nosings) of each stair tread to the top of the guardrail. This ensures the guard maintains the required height along the entire staircase.
Step 4: Check Both Zoning and Building Code Measurements
Don’t assume the same measurement works for every requirement. In Newmarket, zoning usually measures deck height from the average finished grade to the deck floor, while the Ontario Building Code measures guardrail requirements from the finished deck surface to the ground directly below the deck edge.
On sloping properties, those two measurements can differ significantly, so checking both before construction helps prevent costly changes later.
Read More: Cedar vs Pressure-Treated Decks: Which Wood Wins for Your Backyard?
Which Building Code Applies to Your Deck in Ontario?
Two sets of rules apply. The Ontario Building Code sets your guard requirements, while the Town of Newmarket handles permits, setbacks, and inspections.
The Ontario Building Code (OBC 9.8.8)
Guard rules sit in Subsection 9.8.8 and handrails in 9.8.7, and plan examiners quote those numbers directly. The current edition is O. Reg. 163/24, administered under the Building Code Act, 1992 through the Ministry of Municipal Affairs and Housing.
The OBC derives from the National Building Code of Canada, which is why the two look similar. Only the OBC carries force here, so advice quoting the national code is background reading at best.
Town of Newmarket and York Region Requirements
The Town requires a permit for any deck more than 0.6 m (2 feet) above finished grade, and attached decks always need one, as do unattached decks over 10 square metres (108 square feet). The Town’s building and renovating page lists the current criteria.
Under By-law 2010-40, decks between 0.6 m and 3 m can reach 3.6 m into the rear yard but never closer than 2.4 m to the rear property line. Urban Centres properties fall under By-law 2019-06 instead.
Near the East Holland River, on a slope, or beside a wetland, you may need approval from the Lake Simcoe Region Conservation Authority under O. Reg. 41/24, and Oak Ridges Moraine lots carry their own review. Our trusted deck builders in Newmarket check this on the first visit.
Maximum Baluster Spacing and Opening Requirements
No opening in a guard can let a 4-inch (100 mm) ball through, which covers your picket spacing, the gap under the bottom rail, and the space beside your house wall.
The figure comes from child measurements, since a 4-inch gap is too small for a young child’s head. Newmarket has roughly 14,520 residents under 15, per Statistics Canada census data.
Inspectors bring a real 4-inch ball and test each gap, so we keep a 4-inch pipe coupling in the truck and check before booking. Ten minutes saves a $200 re-inspection.
Standard 2×2 balusters sit about three and a half inches apart, leaving half an inch to spare. The gap that fails is usually the last in a run, which is why we lay out from both ends and meet in the middle. Pressure-treated lumber arrives wet too, so a gap set in May can open past 100 mm by August.
| Opening | Maximum |
| Between balusters | 4-inch (100 mm) ball |
| Under the bottom rail | 4-inch (100 mm) ball |
| Beside the house or a post | 4-inch (100 mm) ball |
| Triangle opening at stairs | 6-inch (150 mm) ball |
Read More: Replacing Wood Deck Boards With Composite: Step-by-Step Guide for Homeowners
Climbable Railings and the Restricted Zone
Horizontal boards and cable railings look great in photos, so homeowners keep asking us for them. The obstacle is that the code limits climbable parts between 5.5 inches (140 mm) and 36 inches (900 mm) above your deck.
About 5.5 inches is where a toddler finds a foothold, and 36 inches is as high as a small child can pull up. Once you know those numbers, the failures make sense: a wide bottom rail becomes a step, lattice gives a child toeholds, and horizontal cables work like a ladder however tightly you space them.
One fix keeps the look you wanted. A glass panel on the inside face turns the horizontal parts outside into trim, because the glass does the work. That decision belongs at drawing stage, which is where our professional deck railing and bench installation services start.
Deck Stair Railing Requirements
Under OBC 9.8.7 and 9.8.8, your stairs need a guard against a fall off the open side plus a handrail to hold.
Stair Guard Height
Your stair guard protects the open edge, measured to a line through the front edges of the treads. That line slopes, so a guard reading fine at the top can come up short three treads down.
Handrail Height: 34 to 38 Inches From the Nosing
Handrails belong between 34 and 38 inches (865 mm to 965 mm) above the tread edge. Outside stairs need one past three steps, and stairs wider than 43 inches (1,100 mm) need one on both sides. Confusing guard and handrail height red tags more stairs than anything else.
Continuous and Graspable Handrails
A handrail has to run without a break and stay easy to grip, so a wide flat board on the posts will not pass. That matters here, where nearly 31 percent of Newmarket residents are 55 or older. For parents visiting in February, a rail their hand closes around prevents a fall on an icy step, which is why we often add custom deck lighting solutions.
Stair Baluster Spacing
Stair pickets follow the same 4-inch (100 mm) rule, except the triangle formed by tread, riser, and bottom rail can reach 6 inches (150 mm). It fails when your bottom rail sits too high, and the fix is dropping it closer to the treads.
Wood, Aluminum, Glass, and Composite Railings: The SB-7 Rule
Supplementary Standard SB-7 covers wood guards only, so aluminum, glass, composite, and cable guards need drawings stamped by an engineer licensed with Professional Engineers Ontario.
What Counts as a Wood Guard Under SB-7
A wood guard built within the SB-7 limits follows set rules with no engineer involved. The standard fixes post sizes, spacing, and connections, so your permit clears on the Town’s reference drawings. Our premium pressure treated decking stays inside those limits.
When You Need Engineered Drawings
Step outside wood and you step outside SB-7. Most homeowners find out after the railing reaches the driveway, so the question is better raised while comparing quotes. Compliance paperwork should cover your exact setup, since post spacing changes what the manufacturer tested.
What That Means for Cost and Timeline
Engineered drawings and a stamp usually run $600 to $2,500. Removing an old railing adds $5 to $12 per linear foot, and reinforcing an older frame for glass hardware can add $300 to $1,500. None of this rules out aluminum or glass, which handle our freeze-thaw winters better than painted wood. It is a reason to price the whole job in February, a conversation we have with nearly every family choosing composite decking.
Read More: Composite Decking Installation: How-to, Costs & Pro-tips
Do You Need a Permit to Install or Replace Deck Railings?
Replacing deck boards on solid framing usually needs no permit, but rebuilding a guard does, since a guard counts as structural work under the Building Code Act.
Newmarket charges a $300 flat fee for a residential wood deck permit, plus $100 for a zoning review, both from the Town’s 2026 building permit fee schedule. A Zoning Preliminary Review letter comes first, and skipping it stops your application.
Your elevation plan must show deck height at the highest point, plus guard height and type, before the Chief Building Official signs off. We cover the sequence in our complete guide to deck permits in Newmarket.
Top Reasons Newmarket Decks Fail Guard Inspection
The same problems keep showing up, and nearly all get designed out before anyone picks up a saw.
- Height measured from the framing instead of the finished deck surface
- A 36-inch guard on a deck that passed 1,800 mm at one corner
- A wide bottom rail acting as a step
- Guard posts fastened with deck screws instead of through-bolts and washers
- Notched posts cut too deep, leaving a weak connection
- No blocking behind the rim joist where guard posts attach
- Aluminum or glass installed with no engineered drawings on file
- A handrail set at guard height instead of 34 to 38 inches
- Colour drawings submitted when the Town wants unlocked black and white PDFs
Each costs money. A re-inspection on flagged work runs $200, and pulling a finished guard apart costs several times that. Nearly half the homes here predate 1991, so many guards were built to older numbers, and insurers now flag them at renewal.
If an insurer’s letter brought you here and your framing cannot carry a proper guard, professional deck replacement and removal across York Region beats patching twice.
How We Handle Code Compliance on Every Build
We set your guard height from a measured drop, not a guess, which means walking your yard and recording the deepest point before we draw a line. That habit keeps a 36-inch guard off a 42-inch deck.
Then we prepare the elevation plan your examiner expects, arrange engineered drawings when your railing is not wood, and submit through the Town’s Development Portal. We also meet the inspector at footing, framing, and final, so you never chase paperwork or hear about a problem after your boards are down.
Spring is busiest at the Building Division, where a complete application takes ten to twenty business days; drawings booked in the fall or winter land at the quicker end. Our custom deck design and installation services cover everything from first measurement to sign-off.
Call (416) 333-2366 for a free on-site measurement across Newmarket and York Region, or book a free on-site deck consultation online.
Frequently Asked Questions
Can you build a deck without a railing?
Yes, if your deck stays under 24 inches (600 mm) above the ground. Zoning setbacks under By-law 2010-40 still apply.
How much does a deck railing cost in Ontario?
Wood and aluminum run roughly $75 to $175 per linear foot installed, and glass $130 to $400 before engineered drawings.
Are horizontal deck railings allowed in Ontario?
Only where they leave no foothold between 5.5 inches (140 mm) and 36 inches (900 mm), which an inside glass panel solves.
Do cable railings pass inspection in Ontario?
Horizontal cable usually fails as climbable. Vertical cable under 4 inches (100 mm) passes.
Do I need a permit to replace an existing deck railing?
Usually yes, since a guard is structural. Newmarket Building Services can confirm before you order.
My deck railing is only 32 inches. Do I have to replace it?
An older deck is not automatically illegal, but once you rebuild the guard, current OBC rules apply.
Does a glass or aluminum deck railing need engineered drawings?
Yes, because both fall outside Supplementary Standard SB-7, so you need drawings stamped by an Ontario engineer.
Does a second-storey deck need a 42-inch railing?
Almost always, since it sits well past 1,800 mm. The real drop is what counts, not the storey.
What happens if my deck fails its final inspection?
Your inspector leaves a list of deficiencies to correct before a re-inspection, which costs $200 in Newmarket.
How long does a deck permit take in Newmarket?
Usually ten to twenty business days for a complete application. Spring submissions run longer.
