If you have a metal roof, you have probably noticed that snow doesn’t stay on it for long. That is one of the advantages of a sheet metal roof, but it is also what can cause problems. When a large amount of snow lets go all at once, it can damage gutters, injure someone walking below or ruin landscaping.
That is why we talk about snow stops, and in many situations they are far from an optional accessory.
How does a snow stop work?
A snow stop, also called a snow guard or snow retention bar, is a device fastened directly to the roof. Its job is to hold the snow in place and let it melt gradually, rather than sliding off suddenly and all at once.
They come in several forms. The most common models for metal roofs are tubular bars or perforated plates, installed in horizontal rows across the roof slope. Contrary to what you might think, they do not hold all the snow permanently: they break up and slow down the slides to prevent sudden avalanches.
When is a snow stop really necessary?
It is not mandatory in every case, but some situations make it highly recommended:
- An entrance, walkway or patio below: This is the most common situation. A sudden snow slide in that spot poses a real risk to people.
- Gutters installed along the roof edge: Sliding snow can tear gutters off in seconds. A snow stop effectively protects this drainage system.
- Steep roof with large surfaces: The steeper the slope and the larger the surface, the more snow can build up and come down all at once.
- Close neighbours or adjacent buildings: When the roof edge sits above a vehicle, a fence or a neighbouring structure, a snow guard limits potential damage.
- Local regulations or insurance: Some municipalities or insurance companies may require this type of device, especially in areas where metal roofs are common.
What happens without a snow stop
On a sheet metal roof with no retention device, snow can build up for days before sliding off abruptly. The slide can amount to hundreds of kilos of packed snow and ice. The most frequent consequences are torn-off gutters, damaged vehicles, minor to serious injuries, or damage to structures on the ground.
During a Quebec winter, with heavy accumulations and repeated freeze-thaw cycles, this risk is present practically every season.
What type of building is suited to a metal roof?
Metal roofing suits residential homes as well as commercial, agricultural and industrial buildings. It is particularly well suited to low-slope roofs, large surfaces and regions with harsh winters, which describes most of Quebec.
For homes with more complex roofs (many facets, dormers, chimneys), it is important to hire an experienced installer to ensure a watertight, long-lasting installation.
How are snow stops installed?
Ideally, they are installed at the same time as the roof, but they can also be added to an existing roof. The devices are fastened into the ribs or panels of the metal, depending on the type of roof, with fasteners designed not to compromise watertightness.
The position and number of rows depend on the roof slope, the length of the roof plane and the usual snow load in your region. For an effective installation, it is best to consult a professional who knows the products used on your roof, since fasteners and metal compatibility vary from one system to another.
Which snow guard should you choose for a metal roof?
Some models are designed specifically for sheet metal roofs. Tubular snow bars in galvanized steel are among the most durable and least visible solutions. They work well with corrugated roofs, standing seam panels and other metal systems.
For a standard residential roof, two rows of snow stops are usually enough. For a commercial roof or a large surface, a more detailed assessment may be needed.