When should snow be removed from a roof? There is no universal depth threshold.
Snow depth tells only part of the story. Wet or water-laden snow, wind drifts, ice, roof geometry and building condition may matter more than one measurement.
Monitor accumulation and, above all, the building’s warning signs. When several signs of overload appear, the RBQ recommends evacuation and snow removal regardless of the visible quantity.
Warning signs requiring action
New cracks in interior walls or ceilings.
Interior doors that rub, bind or become difficult to close.
Unusual cracking sounds, ceiling deformation or apparent structural movement.
Highly uneven accumulation, significant drifting or ponding on a flat roof.
Why centimetres alone are not enough
Weight varies greatly between powder, compacted snow, wet snow and ice. Wind can concentrate loads near raised walls, equipment and changes in roof elevation. A single depth rule can therefore create false reassurance.
Flat, sloped and unusual roofs
Vaulted or curved roofs and areas with asymmetrical accumulation deserve particular attention. On flat roofs, drains, overflow scuppers and drainage paths must remain functional; ponding adds load and may indicate deformation or poor drainage.
Remove snow without damaging the building
The RBQ recommends using a contractor with suitable experience and equipment. For light work performed from the ground, a telescopic roof rake reduces fall exposure. Leave a thin protective layer so the membrane or covering is not damaged, and avoid creating a more unbalanced load.
What an inspection can contribute
An inspection documents visible indications such as deformation, cracks, leakage, drain condition, accumulation zones and accessible attic conditions. It does not calculate structural capacity. When stability or roof capacity is in question, an engineer should perform the assessment and determine required measures.
Sources and references
The following sources frame and support this content. The service agreement and the standard applicable to the assignment remain controlling.