Glass railings are common on GTA decks, stairs and condo balconies, and Ontario’s Building Code allows them. The difference is in the paperwork. A wood railing can be built from the code’s standard details, but a glass railing has to be engineered, and the building inspector will usually want proof.
Where a guard is required and how high it must be
The code calls a railing that keeps people from falling a guard. Under Ontario’s 2024 Building Code, a guard is required wherever a walking surface (a deck, landing, porch, balcony or stair) is more than 600 mm above the surface next to it within 1.2 m. On a house, the minimum heights are:
- 900 mm for guards inside the home, including a house with a secondary suite.
- 900 mm for exterior guards where the deck or balcony is no more than 1.8 m above finished ground.
- 1 070 mm for exterior guards higher than that, and for guards the two cases above don’t cover.
- On stairs, height is measured straight up from a line drawn through the front edges of the treads.
Glass follows the same rules for openings and climbing as pickets do. Openings must stop a 100 mm sphere, which in practice includes the gap between the bottom of the glass and the floor, and no rail, clamp or fitting between 140 mm and 900 mm above the floor may make the guard climbable.
What the code says about the glass
For houses and other small buildings, which fall under Part 9 of the code, Article 9.8.8.7 requires glass in a guard to be laminated or tempered safety glass meeting CAN/CGSB-12.1, or wired glass meeting CAN/CGSB-12.11-M. Ordinary glass is not acceptable.
Supplementary Standard SB-13, Glass in Guards, applies to larger buildings designed under Part 3 of the code, such as most condo and apartment buildings. It covers a balcony guard serving a single unit, but not interior guards inside a unit, which follow the house rules above. SB-13 ties the glass type to where the panel sits: glass beyond the floor edge or within 50 mm of it must be heat-strengthened laminated glass, heat-soaked tempered glass is allowed more than 50 mm inward, and tempered glass no thicker than 6 mm only more than 150 mm inward. The glass must also be designed under Part 4, the structural part of the code, and kept out of direct contact with metal.
What an engineering letter confirms
Ontario’s standard guard details, Supplementary Standard SB-7, cover wood guards only. As the City of Markham’s building department puts it, guards of glass, steel or aluminum must be professionally engineered, and proof of the engineered design goes to the inspector before installation. A complete engineering letter for a glass railing covers:
- The guard height and openings for that location.
- The glass type and thickness, and the safety glazing standard it meets.
- The posts, base shoe or clamps, and their spacing.
- The anchors and fasteners, and what they go into: a wood rim joist, a steel stringer or a concrete slab.
- The design loads the guard resists and the standard used to design the glass, which for guards is CAN/CGSB-12.20.
Look closely at frameless designs. The City of Ottawa’s glass guard advisory notes that the glass design standard requires free-standing panels, meaning panels supported only at the bottom, to be capped by a rail running continuously over two or more panels, so the guard still holds if one panel breaks. Other support arrangements can allow a different look, which is a question to settle with the engineer before glass is ordered.
When inspectors ask for it
Expect to need engineering at two points. At permit stage, Vaughan asks for pre-engineered guard or railing details with deck drawings, and Toronto requires an Assumption of Responsibility form from any engineer who seals permit documents. At inspection, Vaughan’s deck inspection notes say guard and handrail connections may need a professional engineer’s involvement, and Markham wants the engineered design before the glass goes in. In Mississauga, replacing or repairing guards on an apartment or condo balcony needs a building permit.
How to avoid delays
- Choose the railing system before the permit drawings are finished, so the engineered details go in with the first submission.
- Build exactly what the letter describes: the same glass, post spacing and anchors. A substitution on site can mean a revised letter.
- Plan for the anchors early. Posts and base shoes need solid framing or concrete at the edge, which is easier to provide before decking or finishes go down.
- In a condo, get property management’s approval and confirm permitted working hours before booking the installation.
- Keep the letter and the glass supplier’s documents with the permit file for the final inspection.
Glass railings from MKC
MKC Group designs and installs custom glass railings for decks, stairs and balconies across the GTA, and every custom glass job comes with a free engineering letter from our in-house engineering department. We prepare the drawings, handle the permit application and build to the approved design, so the letter, the permit and the installation match. MKC is also one of few curved glass suppliers in the GTA. Call (647) 637-6052 for a free estimate.