Navigating Ontario Roof Building Codes

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It might be difficult to follow and comprehend coding requirements, particularly when working on several or large-scale projects. With our brief explanation of the Ontario building code’s ventilation standards, you can safeguard your building’s occupants and guarantee a speedy inspection procedure.

In an effort to improve a building’s energy efficiency by fifteen percent, Ontario has revised its set of ventilation code requirements. The modifications focus on ventilation systems’ heat recovery and offer incentives to increase building airtightness.

The majority of Section 9 of the Ontario Building Code 2020 (OBC) has not changed, but all residential and commercial buildings must have either an energy-recovery ventilator (ERV) or a heat-recovery ventilator (HRV).

What are the Ontario Roof Building Codes

The standards that control the design, construction, and renovation of buildings in Ontario are known as the Ontario Building Code (OBC). To guarantee that it incorporates the most recent developments in building technology and safety, the OBC is revised every five years.

Roofing standards specified by the OBC include the following:

  • Materials for Roofing → These materials need to be strong enough to endure the anticipated loads and weather.
  • Flashing → To stop water leaks, flashing needs to be placed correctly.
  • Ventilation → To avoid moisture accumulation and ice damming, roofs need to be adequately vented.
  • Snow and Ice Loads → Roofs need to be built to resist the amount of snow and ice that is typical for the area.

The following particular demands are listed by the OBC:

A minimum of Class C roof covering is needed.

  • Asphalt Shingles → Unless further overlays are supported by an engineering investigation, an existing asphalt shingle may only have one (1) asphalt shingle overlay laid over it.
  • Eaves Protection → For roofs made of shake, tile, or shingle, eaves protection must be installed. It should reach from the roof’s edge a minimum of 900 mm up the roof slope to a line that is at least 300 mm within the outer wall’s inner face.
  • Roof Pitch → For shingle roofs, a minimum of 4:12 is required.
  • Roof Vents → A minimum of 1 vent must be provided for every 300 square feet of roof space.
  • Snow Guards → If a roof is situated over a public walkway or driveway and has a slope of 10:12 or higher, snow guards must be built.

Remember that the OBC is merely a minimal requirement. Certain localities could have extra specifications when it comes to roofing. For the most recent information on roofing standards, it is usually advisable to check with your local building department.

What are the Specific Requirements for Roof Slope in Ontario

The minimum required roof slope for various roofing materials is specified by the Ontario Building Code (OBC) as follows:

Roofing Material

Minimum Slope

Asphalt shingles


Cedar Shakes


Metal Roofing 


Slate Tile


Clay Tile


Proper ventilation of roofs is necessary to avoid moisture buildup and ice damming, as mandated by the OBC. The following are the minimal ventilation requirements:

  • Ridge Vents → A ridge vent needs to be put in place the whole way around the ridge, or something similar.
  • Eaves Vents → Installing eaves vents at the roof’s eaves requires spacing them no more than 1.2 meters apart.
  • Soffit Vents → Soffit vents are to be positioned at the roof’s soffits, with a maximum distance of 2.4 meters between them.

Remember that these are really the bare minimal needs. Depending on the kind of roofing material you’re using, the size of your roof, and the local environment, you could occasionally need to install extra ventilation.

It’s also vital to remember that, depending on the circumstances, the OBC can have extra guidelines for roof slopes, such as when the roof is over a roadway or public path. To obtain the most recent information on roof slope standards, it is usually advisable to inquire with your local building department.

What are the Ventilation Requirements for Roofs in Ontario

The following minimum ventilation criteria for rooftops are specified by the Ontario Building Code (OBC):

Total Ventilation Area →The overall ventilation space ought to be a minimum of 1/300 of the area covered by the insulated ceiling.

Distribution → There should be an equal distribution of ventilation holes on both sides of the building, with a minimum of 25% of the openings situated at the top and a minimum of 25% at the bottom of the space.

Type of Vents →Vents might be of the roof, eave, gable-end, or any combination of those types.

Installing further ventilation, such as gable or roof vents, maybe something you want to think about if you are worried about ice dams developing on your roof. In order for water to drain correctly, you need also make sure that your gutters and downspouts are clear of debris and clean.

Are there any specific Fire Safety Regulations for Roofs in Ontario

Certain rules for roof fire safety are found in the Ontario Building Code (OBC). The main goal of these standards is to ensure that roofing materials are fire resistant. Based on their ability to withstand fire, roofing materials are grouped into Class A, B, or C categories.

  • Class A: The greatest fire resistance is exhibited by these materials. They work well to prevent exposure to extreme fires.
  • Class B: This group of materials has a modest fire resistance. When compared to Class A materials, they offer less protection.
  • Class C: Although they are the least fire-resistant materials, Class C materials can nonetheless provide some protection from small fire exposure.

Local fire safety laws, the type of building, and its occupancy all influence the choice of roofing materials and their fire resistance rating. As rules might change depending on the usage and location of the building, it is imperative to check with the OBC or local municipal authorities for the most current and detailed information regarding fire safety for roofs in Ontario.