Snow Retention Systems for a Metal Roof

April 3rd, 2014

Installing a snow retention system on your next metal roof can provide protection for the building owner and extra income, credibility and market share for you.

As the winter build-up of snow and ice begins to thaw, and even in the dead of winter in some places, building owners run the risk of a heavy avalanche of snow or ice falling on property or people as it slides off the roof.  You can see “Caution: Sliding Snow and Ice” signs in front of some buildings every year and probably witnessed a YouTube video of this happening.  Deaths and injury occur every year when people are hit by the heavy ice and snow build-up.Sliding Snow on a Metal Roof

Anticipating and addressing this liability with your customer can provide them with valuable protection from the risk of snow and ice damaging property or even killing a person and could establish you as the contractor that goes the extra mile for his customer.  It’s not a time consuming or expensive add-on when you follow some simple guidelines and understand the issues involved.

Metal roofs have different properties from other roofs when it comes to sliding snow and ice; namely, metal roofs shed it quickly with little warning!  This is partly due to the lack of friction provided by metal as well as its conductive properties.

There are several “Don’ts” when it comes to putting any type of snow retention on a metal roof:

  • Be wary of gluing snow guards on the roof.  Adhesive-attached snow retention must be installed on perfectly clean surfaces and at certain temperatures.  Even when applying them correctly, glued-on snow retention devices they are vulnerable to release during freeze/thaw cycles.  Mechanically fastened snow fences are a better and less labor-intensive method
  • Do not use dissimilar metals.  If your roof is steel, use steel snow retention.  Don’t put copper or aluminum on a steel roof and vice versa.  By mixing the metals, you risk galvanic action (corrosion).
  • Never penetrate the roof system!  This will void the manufacturer’s warranty on the metal roof.
  • Do not assume that you can place one or two rows of snow retention near the eave of the roof.  This is a common mistake and can result in snow fence failure due to using a system that was not engineered.  When the snow releases on this type of amateur design, it can take penetrations, gutters and the snow retention devices off the roof.  Sometimes whole panels slide off.  Various factors must be considered when safely laying out your snow retention


There are some basic “Do’s” to a good snow retention system on a metal roof:

  • Use systems that clamp on seams.   Besides maintaining the manufacturer’s warranty by not penetrating the roof system, clamps with 3-4 ” of contact with the rib will provide more security for the snow fence system
  • Clamps should attach under the hem on the seam.  This prevents twisting and detachment when the snow fence is under pressure from the weight of snow and ice.
  • Part of the clamp should sit on the base of the metal panel.  This helps keep the clamp and rib stable and upright, preventing the rib from bending sideways.

Single and Double Rail Clamp On Snow Fence, Nita Lake Lodge, Whistler Canada 2011 16

The Importance of an Engineered Layout

Snowload -Either listed on the plans or obtained from the local building department.Engineering the snow retention system is of paramount importance to protect the roof system, the owner and you.  Don’t be afraid of the word “engineering!”  Some reputable roof snow retention companies provide this free.  All it takes is gathering a few facts:

  • Roof Slope – Obviously a 12/12 sloped roof will need a different layout than a 4/12 but the actual layout should never be left to guesswork.
  • Rib Type – Different clamps are designed to work with different rib types.
  • Rib Spacing – Rib spacing affects the number of clamps needed.  The strength of the snow fence depends on how far apart the clamps are spaced
  • Method of Panel Attachment – If a panel is attached with a clip which does not stop vertical movement, the snowload can cause the panel to fall off the roof.  Knowing how the panel is attached will affect what type of snow retention to use.
  • Eave to Ridge Length – This affects how much snow that area will be supporting which will determine the number of snow fences needed up the span from eave to ridge.


Correctly installed snow retention is a good idea for the owner because it protects property and people from significant damage or even death.  By adhering to a few simple Do’s and Don’ts and using an engineered layout, it could also be a significant way to enhance your business.

Terry Anderson has been in the roof consulting and roof accessory business for over 30 years.  He is a Registered Roof Consultant, member of TRI and co-author of Concrete and Clay Tile Roof Design Criteria Manual for Cold and Snow Regions and the owner of several roof accessory patents including the original Snow Bracket and Ridge Riser®.  His company, TRA Snow and Sun, Inc. manufactures snow retention devices for all types of roofs, solar mounting systems, and flexible ventilation and flashing products.

Published: Metal Construction News April 2014