Roof Snow Loads and Ice Dam Formation
A reference on the conditions that lead to structural snow load concerns and ice damming on sloped residential roofs in Canadian climates.
Articles on Roof Snow and Ice Dams
Detailed reference material covering ice dam mechanics, safe snow removal, and ventilation approaches suited to Canadian winters.
How Ice Dams Form on Canadian Roofs
The temperature cycle behind ice dam development, why eaves are most vulnerable, and how heat loss from living spaces drives the process on sloped roofs.
Read article →
Safe Roof Snow Removal Guidelines
When accumulated snow warrants removal, how to assess load risk from ground level, and which methods carry the least risk to roofing materials and personal safety.
Read article →
Attic Ventilation and Ice Dam Prevention
How attic airflow design reduces the warm-deck conditions that cause snowmelt, and what the National Building Code says about ventilation ratios for cold climates.
Read article →Understanding Snow Load and Ice Damming
These two issues — structural snow load and ice dam water infiltration — are related but distinct concerns for Canadian homeowners.
Structural Weight vs. Drainage
Snow load refers to the compressive weight of accumulated snow on the roof structure. Ice dams primarily cause water damage through infiltration, not structural overload, though heavy ice ridges can add significant mass.
The Role of Attic Temperature
In most ice dam scenarios, the upper portions of the roof are above 0°C from escaping interior heat, while eaves remain sub-zero. This gradient drives the melt-refreeze cycle characteristic of ice dam formation.
Climate Zones Across Canada
Ground snow load figures vary considerably between coastal BC, the Prairie provinces, and the St. Lawrence lowlands. The NBC's climatic data tables map these differences to guide local design standards.
Contact
Questions or corrections regarding the content on this site can be submitted using this form. Responses are not guaranteed for all inquiries.
For urgent roof safety concerns, contact a licensed roofing contractor or structural engineer in your province.
Disclaimer: The information on this site is provided for general educational reference only. It does not constitute structural, engineering, or safety advice. Always consult a licensed contractor or engineer before making decisions about your roof.