Does your roof need snow removal?
Most pitched roofs in Calgary do not need snow removed. A sound roof in good repair is built to carry the snow a normal winter delivers, and chinooks often melt a good share of it within days. Getting on a roof to clear snow that would have been fine adds risk to the roof and to whoever is up there.
There are real situations, though, where snow should come off or at least be reduced:
- Heavy, wet spring snow. March and April storms can drop dense snow that weighs far more than mid-winter powder.
- Deep drifts against a second-storey wall, a dormer, a chimney or a parapet, concentrating weight on one part of the roof.
- Flat and low-slope roofs, where snow does not slide off and meltwater has nowhere quick to go.
- Garages, sheds and additions, often built lighter than the main house, with snow sliding or drifting onto them from the higher roof.
- Older or already damaged roofs with soft decking or past water damage.
- Warning signs inside, such as sagging ceilings, doors that suddenly stick, new drywall cracks or unusual creaking.
If none of these apply, the honest answer is usually to leave the snow where it is and keep an eye on it.
Why Calgary snow is different
Calgary snow changes character through the season, which is why roof loads are hard to judge by depth alone. A foot of cold, dry January snow is light; the same depth of wet spring snow, or snow that has melted and refrozen, is much heavier.
Chinooks are the big local factor. Warm westerly winds can push Calgary above freezing, sometimes past 10°C, for days in mid-winter. Snow on the roof softens, settles and partly melts, then refreezes into dense, icy layers when the cold returns. A few of those cycles turn a light snowpack into something closer to a slab of ice.
Wind matters too. Snow blows off the exposed side of a roof and piles up on the sheltered side, against walls and behind parapets. One slope can look nearly bare while another carries a deep drift.
Snow load warning signs
The clearest warning sign of too much snow on a roof is a change you can see or hear inside the building. Roofs rarely fail without some signal first, so know what to watch for in a heavy winter:
- Sagging in a ceiling, or a visible dip along the roof line from outside.
- Doors and windows that suddenly stick or will not latch, especially upstairs and on interior walls.
- New cracks in drywall or plaster, often near door frames or where walls meet the ceiling.
- Creaking, popping or cracking sounds from the attic or roof structure.
- Water stains or leaks appearing during a melt.
- Bent or shifted framing visible in the attic or garage.
The risks of DIY roof snow removal
Shovelling your own roof is one of the more dangerous winter chores a homeowner can take on. The hazards stack up quickly:
- Falls. Snow hides skylights, vents, roof edges and the ice underneath.
- Ladders on ice. A ladder on frozen ground or against an icy roof edge can kick out without warning.
- Power lines. Service lines often run near the roof edge, and metal ladders and roof rakes conduct electricity.
- Damaged shingles. Cold asphalt shingles are brittle. Metal shovels and ice picks crack them and break their seals.
- Cut membranes. On a flat roof, one careless shovel stroke can slice the membrane and start a leak.
- Sliding snow. Snow on metal roofs can release as one heavy sheet and take a person or a ladder with it.
- Uneven removal. Clearing one side or one section can leave the load unbalanced on the parts still covered.
How professional roof snow removal is done
Good roof snow removal takes off enough weight to protect the building without harming the roof surface. It is slower and more careful than shovelling everything off:
- Safety setup first. Fall protection, secure access and a clear, marked drop zone below.
- Leave a protective layer. A thin layer of snow stays on the roof so tools never touch shingles or membranes.
- Use the right tools. Plastic shovels and pushers instead of metal blades and ice picks.
- Remove drifts evenly. The deepest drifts come down first, in a balanced pattern, so no area is left carrying extra weight.
- Keep drainage open. On flat roofs, snow is cleared back from drains and scuppers so meltwater can leave.
- Protect what is below. Walkways, entrances, vehicles, landscaping and air conditioning units are kept clear of falling snow and ice.
- Note any trouble. Damaged shingles, loose flashing or ice building at the eaves are pointed out so you can decide what to do.
Flat roofs, garages and commercial buildings
Flat and low-slope roofs are where snow load matters most, because snow stays where it lands and drifts wherever the roof creates shelter. Inner-city infills, detached garages, additions and commercial buildings all fall into this group.
The common problems on these roofs are:
- Drifting at parapets and rooftop units, where snow collects deeply against low walls, mechanical units and changes in roof height.
- Ponding. When a chinook melts snow but drains or scuppers are frozen or buried, water pools on the membrane and can refreeze into heavy ice.
- Membrane damage. Shovels, picks and foot traffic can cut or puncture single-ply and modified bitumen membranes in the cold.
- Lower roofs beside taller ones, which catch snow sliding or blowing off the higher roof.
Property managers should know where drains and scuppers are before winter, keep rooftop access clear, check the roof after big storms and chinooks, and make sure anyone clearing snow knows where seams and penetrations sit.
Snow, ice dams and leaks
Snow on its own does not cause most winter roof leaks; ice dams do. Heat escaping from the house melts snow on the upper roof, the water refreezes at the colder eaves, and water pooling behind that ice backs up under the shingles. Chinooks speed the whole cycle up.
Clearing the lower few feet of a roof can reduce the meltwater feeding an ice dam, but once ice has formed it needs a different approach; see our ice dam removal page. Because attic heat loss is the root cause, our roof ventilation page explains how airflow and insulation keep the roof deck cold and even.
Using a roof rake safely from the ground
A roof rake can be a reasonable homeowner tool for the lower edge of a single-storey roof, as long as it is used from the ground:
- Stay on the ground. Never use a roof rake from a ladder or while standing on the roof.
- Single-storey eaves only. If you cannot reach comfortably from solid footing, leave it.
- Look up first. Check for power lines and keep the rake well clear of them.
- Do not scrape to bare shingles. Leave a few centimetres of snow so the rake does not tear or loosen shingles.
- Pull gently, in small amounts, standing to the side rather than directly under the edge.
- Leave the ice alone. Do not chip or hammer at ice along the eaves.
Reducing snow problems long term
The best way to avoid roof snow removal is to fix what makes snow a problem in the first place:
- Snow guards on metal roofs hold snow in place so it melts gradually instead of sliding in one sheet onto walkways or lower roofs.
- Ventilation and insulation keep the roof deck cold, cutting down on uneven melting and ice at the eaves.
- Better drainage on flat roofs, with drains and scuppers placed and maintained so meltwater leaves during a chinook.
- Fewer rooftop obstructions where possible, since every unit, curb and change in height gives drifts a place to build.
- Well-sealed penetrations. Trapped meltwater often finds its way in around chimneys, so sound chimney flashing matters in snow season.
What affects the cost of roof snow removal?
The cost of roof snow removal depends on how much snow there is, what kind of roof it sits on, and how safely it can be reached. The main factors are:
- Roof size and shape, including dormers, valleys and multiple levels.
- Pitch and height. Steep, tall roofs need more safety setup and time.
- Roof type. Flat membranes and metal roofs call for extra care.
- Snow depth and density. Wet spring snow and icy chinook layers are slower to move than dry powder.
- Drifts and ice against walls, parapets and rooftop units.
- Access and what needs protecting below.
Not sure where to start? Book a free inspection or contact us and tell us about your roof and the snow on it.