How to Install Snow Guards on a Metal Roof: Layout, Clamps and Placement
Metal is slick, and snow can release all at once. Staggered rows of guards hold it in place so it melts and sheds in small amounts.
- Advanced
- 2 to 6 hours
- Updated
The short answer
Snow guards hold snow on a metal roof so it melts off gradually instead of releasing in a sheet. Place rows above doors, walkways, gutters and lower roofs, starting near the eave about 12 to 24 inches up, and stagger guards in rows spaced roughly 4 to 8 feet apart up the slope. Use clamp-on guards on standing seam and fasten guards through ribs on exposed-fastener panels.
A shingle roof grips snow. A metal roof does not. The panels are smooth, dark colours warm the snow at the surface, and the hidden fasteners leave nothing to catch on, so a thick snowpack can let go all at once. A sheet of snow and ice can weigh hundreds of kilograms. It can tear off gutters, dent cars, damage plants and injure people walking below.
Snow guards do not stop snow from ever sliding. They break up the load so it sheds in small pieces, or they hold it until it melts. They are most important above doors, walkways, driveways, lower roofs, vents and gutters. In the Fraser Valley snow is occasional, but heavy and wet snow does fall, and at Hope and up the canyon it can stay for days. Whether snow guards are needed is also a code question in some municipalities.
Guards attach in different ways depending on the panel. See metal roof panel types for the profiles, and install standing seam for how seams work.
Tools
- Tape measure and chalk line
- Torque wrench or screwdriver as the clamp maker specifies
- Impact driver
- Level or string line
- Caulk gun
- Fall protection equipment
Materials
- Snow guards or snow rails matched to the panel profile
- Clamps, set screws or fasteners supplied by the guard maker
- Butyl or polyurethane sealant for fastened guards
- Touch-up paint
- Panel cleaner for the mounting spots
Safety first
- Work on a dry, clear roof. Never work above people or entrances, and cordon off the ground below. A dropped tool or a guard can hit someone.
- Snow and ice remaining on the roof make it lethal. Do not install guards while there is snow or frost on the panels.
- WorkSafeBC requires fall protection at 3 metres (about 10 feet) and wherever a fall of any height could cause serious injury.
Step by Step
Step 1: Identify where snow slide is a hazard
Look at doors, walkways, driveways, decks, meters, vents, satellite dishes, lower roofs and gutters. Also look at where snow from the upper roof lands on a lower roof, since a sliding load on a lower roof can overload it or slide again. A valley that runs to a walkway is a hazard.
Mark these planes on a roof sketch. You may only need guards on some planes. Some owners choose to protect the whole roof.
Step 2: Choose guards that match the panel
On standing seam, clamp-on guards grip the seam with set screws, so no holes are made in the panel. They must be rated for the seam shape and gauge, and the set screws should be stainless or coated and installed to the manufacturer's torque so they do not scar the seam. On ribbed exposed-fastener panels, guards are screwed through the rib or the flat into the purlin, with sealant or a gasket under the base.
Guards come as individual blocks, bars, pad types and continuous rails. Individual guards break up the slide and let water through. Continuous rails and pipe-style systems hold more load and look different. Choose by snow load and appearance, and check the manufacturer's load tables.
Step 3: Plan the layout: where rows go and how far apart
The first row goes just above the eave, or above the wall line at a door, so the snow is held near the bottom. More rows are needed on long, steep roofs and in heavy snow zones. The spacing of rows and guards within a row depends on the snow load, the slope and the panel. A long roof in a heavy snow zone may need a row every 4 feet, while a mild one needs only a row near the eave.
Stagger the guards in alternate rows so snow cannot run straight between them. On a standing seam roof, put a guard on every second or third seam in a row as the maker specifies, and offset the next row. Follow the manufacturer's layout tables. Ground snow loads for your area are published by the building code, and they drive the number. Ask your building department or a designer for the value.
Watch out: Snow retention is load-bearing. In heavy snow areas an engineer or the guard maker's table should set the number of rows. Too few guards can load individual ones past their rating.
Step 4: Mark and prepare the mounting spots
Snap a line across the roof for each row, using the same distance from the eave at both ends. Check that seams or ribs are straight and that there is no loose sealant or dirt where a clamp will grip. Mark each guard location on the line.
Keep guards away from panel ends and trims by the distance in the manual. Guards near an eave or valley see the largest loads.
Step 5: Install the guards to the maker's torque or fastening
Set each clamp square on the seam and snug it, then tighten the set screws to the specified torque. Too loose and the guard slides, too tight and it can scar the seam or deform it. Use the right tool and check a few with a torque wrench. See metal roof screws for fastener technique on through-fastened guards.
For fastened guards, drive screws into the purlin or solid deck, not just the thin panel. Put sealant or a gasket under the base and press it flat. Fill any stray holes with sealant.
Step 6: Stagger the rows and check alignment
Step back and look at the roof from the ground. Rows should be parallel to the eave and uniform. Guards should line up evenly across the roof. Any bunching or gaps should be fixed now.
Keep guards away from ridge caps and valleys unless the maker specifies otherwise.
Step 7: Protect the gutter and plan for maintenance
A gutter under a metal roof takes a lot of abuse. Guards just above it reduce the slide, and strong hangers at closer spacing, often 24 inches or less, help. Some roofs in heavy snow have no gutter on slide-prone edges.
Inspect guards every year before winter. Check that clamps are tight, that fastened bases are sealed and that no guards have shifted. See eave trim and closures for the gutter interface.
Snow Country Notes: Hope and the Canyon
Heavy, wet snow is the norm at Hope and up the Fraser Canyon, and it often falls on a roof that is already cold. That is the worst case for slides: dense snow on cold metal can release in big slabs. Whether you need guards is a site decision, and in these areas a designer or the guard maker's load tables should be used rather than a rule of thumb. The ground snow load in the building code is the starting number.
Guards, Rails and Doing Nothing
Not every metal roof needs guards. Steep roofs over lawn, where snow can fall freely and harmlessly, often go without. Low-slope roofs may hold snow by themselves. The risk is where falling snow meets people, cars or property. In those spots, guards are cheap insurance and, in some municipalities, required.
Common Mistakes
- Skipping guards above doors and walkways on a slick panel.
- One row only on a long roof, leaving the snow above free to build a slab.
- Not staggering the guards so snow runs straight between them.
- Overtightening clamps and scarring or deforming the seam.
- Fastening through-rib guards into the thin panel instead of the purlin.
- Installing on a snowy or frosty roof.
- Hanging a weak gutter below a slide zone.
When to Call a Professional
Installing guards means working at the eaves of a slick roof and over entrances. If the roof is steep, high or has snow or ice, use a roofer. For heavy snow areas, a designer or engineer should set the layout.
If snow has already slid and damaged gutters, vents or structures, a roofer can repair the damage and plan guards in the same visit.
Fraser Roofing does free roof inspections across the Fraser Valley, from Hope to Abbotsford. See our Metal Roofing service or the towns we cover.
How to Install Snow Guards on a Metal Roof: Questions
Do I need snow guards on a metal roof?
Not always, but you need them wherever falling snow could hurt people or damage property, such as above doors, walkways, driveways, gutters and lower roofs. Metal is slick and snow can release in one sheet. In heavy snow areas like Hope and the canyon, guards are strongly recommended. Check with your local building department for any requirement where you live.
How far apart should snow guards be on a metal roof?
The first row goes near the eave, about 12 to 24 inches up, then additional staggered rows roughly 4 to 8 feet apart up the slope, closer for heavier snow loads and steeper roofs. Within a row, guards go on every second or third seam or at the maker's spacing. Follow the manufacturer's load tables.
Can snow guards be installed without drilling the roof?
On standing seam, yes. Clamp-on guards grip the seam with set screws and make no holes in the panel. On exposed-fastener panels, guards are usually screwed through the rib or flat, sealed at the base. Clamp-on guards must match the seam profile and be tightened to the maker's torque.
What is the difference between snow guards and snow rails?
Snow guards are individual blocks or pads that break up snow so it sheds in small pieces. Snow rails are continuous bars or pipes across the roof that hold back more snow and ice. Rails take heavier loads but are more visible and cost more. The right choice depends on snow load and appearance.
Related Guides
All Metal Roofing guides|The full How-To Library
This guide is general education. Always follow the product manufacturer's installation instructions, the BC Building Code and WorkSafeBC requirements, which take priority over anything written here.
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