If you’ve recently had spray foam insulation installed in your Toronto, Ottawa, or Hamilton home—or you’re planning to—you might be wondering: does it need to be covered? The short answer is yes, in most cases. Ontario Building Code Section 9.10.17.10 requires spray foam insulation to be protected with a thermal barrier when installed in occupied spaces. This guide explains when coverage is required, what qualifies as acceptable protection, and why it matters for your home’s safety and compliance.

What Does the Ontario Building Code Say About Spray Foam Coverage?

Section 9.10.17.10 of the Ontario Building Code specifically addresses “Protection of Foamed Plastics.” Spray foam insulation—whether closed-cell or open-cell—is classified as a foamed plastic material. According to the code, these materials must be separated from interior living spaces by an approved thermal barrier.

The most common thermal barrier is ½-inch gypsum drywall (standard drywall). This material has been tested and approved because it provides adequate fire resistance and delays ignition in the event of a fire. In most residential applications across the Greater Toronto Area, this means your spray foam will be covered by the drywall that finishes your walls and ceilings.

However, the code does allow for alternative thermal barriers in certain situations—such as spray-on intumescent coatings—provided they meet the fire-resistance requirements outlined in OBC sections 9.29.4 through 9.29.9.

When Is Spray Foam Required to Be Covered?

The coverage requirement applies primarily to occupied spaces—areas where people live, work, or spend regular time. This includes:

Interior walls and ceilings in living rooms, bedrooms, kitchens, and hallways
Basement insulation on foundation walls in finished basements
Attic insulation in attic spaces converted to living areas (not unfinished attics)
Bonus rooms, home offices, and other conditioned spaces

In these areas, exposed spray foam poses a fire risk. When ignited, uncovered foam can release toxic smoke and contribute to flame spread. The thermal barrier (typically drywall) slows ignition and gives occupants critical time to evacuate.

Are There Exceptions Where Spray Foam Doesn’t Need to Be Covered?

Yes. The Ontario Building Code allows spray foam to remain exposed in certain unoccupied or non-conditioned spaces, including:

Unfinished attics: If your attic is not used as living space and is only accessed for maintenance, spray foam on the underside of the roof deck can remain exposed in many cases.
Crawl spaces: Spray foam applied to crawl space walls or band joists typically does not require a thermal barrier, as these areas are not occupied.
Rim joists and band boards: These areas between floors are usually enclosed by framing and flooring, so additional coverage is not always required.
Utility rooms and mechanical spaces: Some unfinished basements or utility areas may not require coverage, depending on use and code interpretation by your local building inspector.

It’s important to note that even in these exceptions, local building inspectors have the final say. Code interpretation can vary slightly by municipality—whether you’re in Toronto, Mississauga, Brampton, or Oakville—so always confirm requirements with your local authority before leaving spray foam exposed.

What Qualifies as an Approved Thermal Barrier?

The Ontario Building Code specifies several materials that meet thermal barrier requirements:

½-inch gypsum drywall: The most common and cost-effective solution
Oriented strand board (OSB): Can be used in certain applications
Plywood: Acceptable in some non-living spaces
Intumescent coatings: Spray-on fire-resistant coatings approved for foamed plastics (less common, used in specialized applications)

In most residential projects across Ontario, ½-inch drywall is the go-to choice. It’s affordable, readily available, and meets code requirements without additional testing or approval.

Why Does This Requirement Exist?

The thermal barrier requirement exists to protect building occupants. Spray foam insulation is an excellent material for energy efficiency—it air-seals, insulates, and prevents drafts better than most alternatives. However, like all foam plastics, it is combustible.

In Ontario’s climate—where winter temperatures regularly drop below -20°C in Toronto and Ottawa—homes rely heavily on heating systems. The risk of electrical faults, furnace malfunctions, or other ignition sources means fire safety is a priority. A thermal barrier:

Delays ignition: Gives occupants time to detect and respond to fire
Reduces flame spread: Slows the rate at which fire can travel through walls or ceilings
Limits toxic smoke: Prevents foam from releasing harmful gases into living spaces

This requirement is not unique to Ontario—it’s based on decades of fire safety research and is consistent with building codes across Canada and the United States.

What Happens If You Don’t Cover Spray Foam When Required?

Leaving spray foam exposed in occupied spaces when coverage is required can lead to several problems:

Code violations: Your home may fail a building inspection, delaying occupancy or resale
Insurance issues: Some insurers may refuse coverage or increase premiums if code violations are discovered
Safety risks: Increased fire hazard and liability if an incident occurs
Resale complications: Non-compliant work can complicate home sales and reduce property value

If you’re working with a licensed contractor—like the team at Spray Foam Kings—they will ensure all installations meet Ontario Building Code requirements. Reputable contractors plan for thermal barriers as part of the project scope and coordinate with drywallers to complete the work properly.

Does Closed-Cell Spray Foam Act as a Vapor Barrier?

Yes. Closed-cell spray foam has a very low permeability rating and functions as both an insulator and a vapor barrier when applied at sufficient thickness (typically 2 inches or more). This is one of its key advantages in Ontario’s climate—it prevents moisture migration through walls and ceilings, reducing the risk of condensation and mold growth.

However, acting as a vapor barrier does not eliminate the need for a thermal barrier. The vapor barrier function relates to moisture control, while the thermal barrier requirement relates to fire safety. Both are important, but they serve different purposes under the building code.

Should You Hire a Professional for Spray Foam Installation?

Absolutely. Spray foam insulation requires specialized equipment, training, and knowledge of building codes. A professional contractor will:

Ensure proper coverage and R-value for your climate zone (Ontario requires R-50+ for attic insulation in most cases)
Plan for required thermal barriers and coordinate with other trades
Apply foam safely, with appropriate ventilation and curing time
Pull necessary permits and arrange inspections
Provide warranties and documentation for future reference

DIY spray foam kits are available, but they rarely match the performance, safety, or code compliance of professional installations—especially in retrofit projects where air sealing and moisture management are critical.

Ready to Insulate Your Ontario Home the Right Way?

At Spray Foam Kings, we’ve been insulating homes across Toronto, Ottawa, Hamilton, and the Greater Toronto Area for years. We know the Ontario Building Code inside and out, and we make sure every installation is safe, compliant, and built to last.

Whether you’re insulating a new build, retrofitting an older home, or upgrading your basement or crawl space, we’ll guide you through the process—from initial assessment to final inspection.

Call us today at 647-641-6881 or visit our Google Business Profile to see what our customers are saying. Want to learn more about rebates and financing? Check out our rebates page or contact us for a free quote.

Don’t leave your home’s safety and efficiency to chance. Let Spray Foam Kings handle your insulation the right way—code-compliant, professionally installed, and built for Ontario’s toughest winters.