FH 5.6: Ice Buildup on the Roof

Roofs and attics shall be constructed with sufficient ventilation (if designed to include ventilation), air sealing and thermal insulation to minimize ice buildup on roof surfaces.

One-Year - Work and Materials One-Year – Ontario Building Code Violations Two – Year – Ontario Building Code Health and Safety Violations • A complete list of “CONDITIONS NOT COVERED UNDER WARRANTY” is on p.15 of the Guidelines.

Ice buildup resulting from a Building Code violation or a defect in work or materials supplied by the builder shall be repaired.

Ice buildup on roofs may occur when the roof surface is warm enough to melt the snow, but the air temperature is cold enough to re-freeze the melt water. The roof surface temperature may increase due to building exposure, orientation, or elevated attic temperatures resulting from the insulating effects of snow accumulation on the roof, air leakage and/or heat loss from the interior of the building into the attic space. Precipitation patterns and roof design may also contribute to snow and/or ice buildup on roofs. Where ice buildup on the roof is the result of a Building Code violation or a defect in work or materials provided by the builder, the defect shall be repaired. For a list of contributing factors to ice buildup on roofs that are regulated by the Building Code, see Appendix A7 “OBC Requirements & Construction Considerations to Minimize Ice Buildup on Roofs." Eavestroughs and downspouts should be kept clear of debris and dirt by the homeowner to ensure efficient water flow and drainage from the roof. This prevents water accumulation that can freeze and contribute to the formation of ice buildup on the roof. Cleaning these components is recommended during both fall and spring as part of the home maintenance routine. For articles in the Guidelines on conditions relating to these components, please refer to the “See also” section below. For areas in the province with frequent and heavy snowfalls, where snow removal from roofs is part of winter home maintenance, professional removal of snow accumulation can help reduce the likelihood of ice buildup and water ingress into building assemblies. For water leakage or leakage resulting from ice buildup on roofs, please see section 5.4 “Roof or Flashing Leaks.” See also: 5.4 ROOF OR FLASHING LEAKS 5.5 INADEQUATE ATTIC VENTILATION 5.22 EAVESTROUGHS OR DOWNSPOUTS NOT PERFORMING PROPERLY 5.24 SKYLIGHT LEAKS 8.7 INSUFICIENT INSULATION 13.2 ROOF FLASHING LEAKS AT CHIMNEY Appendix A7 “OBC Requirements & Construction Considerations to Minimize Ice Buildup on Roofs". Notes Words in italics are defined in the “TERMINOLOGY” section on page 19. This article was revised on May 24, 2024.