How to Protect for Heavy Snow Load?

Every winter; roofing contractors receive some inquiries from clients that are concerned about snow load on their roofs. Usually, such requests come after a heavy snowfall event, or when excessive ice accumulation can be observed from the ground.

As a result; a home or business owner contacts a roofing specialist to determine what can be done to remove the snow load and or ice buildup from their roof.

For those people that have metal roofs, rural properties, or commercial flat roofs; the concept of removing snow load is a more familiar idea. In cities with residential areas; it would seem that many people don’t consider the activity until a point of near peril; save for experienced property managers, or facility managers that have an understanding of the ramifications when one does not manage such potential perils.

Let’s face it, most people don’t think about their roof particularly in the frozen winter. But for the people that have ever experienced ice damming or some form of winter leaking; snow and ice removal can be the first defence to mitigating interior damage.

Also to note is that the GTA has not received the volume of snow that we had experienced years ago, and, unlike our neighbours to the north. So it is logical that many would not consider the activity whatsoever.

The fact is that even with the volumes of snow that we do receive, it is a good idea to have a strategy in place, in advance of such events. When the GTA does experience heavy snowfalls, roofing contractors get booked up very quickly. Some roofing contractors that only operate seasonally; often do not have the manpower to service such requests in the winter period. As a result; prospective roofing clients should ask if their roofing service provider operates throughout the winter season and provides winter services.

Related Content: Are Flat Roofs Good in Toronto’s Snowy Weather

Something else to think about is the weight of snow. As snow compacts, and in respect to the moisture content of snow; one cubic foot of snow can weigh as much as twenty pounds. According to some, the average weight of snow can be calculated at one and a quarter pounds per inch.

If we think of a 300 square foot flat roof as an example ( typical for many Toronto downtown homes); that has accumulated one foot of snow over time, which has melted and re-frozen, and compacted; that could represent 4,500 lbs. of additional weight (load), that the roof structure must withstand.
Consider further that many of the older flat roofs were not built to modern-day building code standards, with roof joists being smaller than what would be specified today.

A result could be undulation of the roof deck, or worse if, for example, the flat roof had multiple waterproofing layers on top. In the U.S., a famous American Wholesale operation experienced the complete collapse of a steel decked flat roof structure under the weight of accumulated snow. The national news stations carried the story.

As a result; that company mandated a program for all of their locations to have a roof snow removal contract in place for every branch. While the cost to that corporation may be viewed as high; the cost resulting from construction rebuilding, customer lawsuits, lost business, and the negative press was likely much higher.

With that representing the extreme end of the spectrum, for most homeowners, the objective would simply be to have prepared for routine removal of excess snow load from their roof.

For some homeowners, it can be as simple as purchasing a snow rake; which extends to permit accessing built-up snow from the ground. Snow, which typically accumulates near the eaves edge of the roof as it melts due to sun or interior heat loss; is the most important area of snow to remove on sloping roofs.

For homes or buildings which are taller or steep in pitch, it is better advised to enlist the services of a roofing contractor who is properly insured, and whose workforce is trained in the safe removal of snow and ice, and who will not damage the roof covering itself.

Sloping roofs that have a shallow pitch may be more prone to receive accumulated weight from the snow. Steeper sloped roofs tend to shed snow more quickly, but the accumulated snow tends to either a) build-up from the guttering (often resulting in ice dams), or b) avalanche off the surface of the roof (such as with metal roofs).

Other strategies on sloped roofs can include the use of snow guards or snow rail systems which are designed to trap snow from avalanching to the ground below. These are a particularly good idea where there is potential for snow or ice to fall onto sidewalks, public walkways, or neighbour’s pathways, where falling snow or ice can cause damage to vehicles or worse people.

It is a sensible idea for commercial building owners to have a program in place for removing snow from their flat roofs. Beyond the obvious reason of getting rid of excessive snow load; those buildings which have older waterproofing assemblies can be vulnerable to water ingress.

Imagine that accumulated snow can drive up underneath perimeter metal flashings, or ice can block drains which prevent the under-lying, meltwater from getting off the roof. This results in even more load. and when refreezing; can serve to tear open the waterproofing membrane itself. Newer flat roofs will be considerably less vulnerable to such an event.

Related Content: The Pros and Cons of a Roof Replacement During the Winter

Residential flat roofs benefit from the same principals involving the prudent removal of excess snow load. For homeowners attempting such work themselves; using plastic shovels void of a sharp blade edge is the preferred tool for removal. Also to watch is where snow is being thrown from the roof. It is therefore a good idea to appoint a ground person whom can direct such an activity safely. An important safety tip is to avoid getting close to the edge of a flat roof, where a sudden slip could result in disaster. As always, such work should be designated to insured and experienced professionals as the best and safest way to resolve such situations.

Costs for snow and ice removal can vary by company, by region, and by circumstances unique to each particular building. As an example; once a large volume of snow is removed from a commercial roof. The large piles of snow must be plowed away from the lot or sidewalk areas. Similarly, a house with limited or narrow access may have to have the snow removed in stages.

Prices can range from several hundred dollars for residential homes, to several thousand dollars for large commercial buildings; but when one considers the cost of a structural loss, interior damage, or injury; it soon becomes clear that the cost pales by comparison.

To learn more about winter snow removal, winter roofing work, or ice remediation contact AVENUE ROAD ROOFING® or visit us at