Metal roof with no snow guards, Poughkeepsie, NY (C) Daniel FriedmanSnow Guard Building Codes & Standards
     

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Snow retention system building codes?

This article discusses standards & codes for snow retention system and answers "no" to the simple question of is there a snow retention system buiding code.

This article series illustrates types of snow guards or snow brakes or other snow retention devices used on metal, rubber, asphalt, and slate roofs and we explain and illustrate in photographs just how and where these devices are attached to building roofs. We give the reasons for snow & ice retainer use and their history.

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Is there a Snow Retention System Building Code?

Metal roof snow brakes - Bard College (C) Daniel Friedman

The short answer: no.

A snow and ice retention system that mounts to a standing seam metal roof by connecting to the roof covering has to resist the forces of snow and ice pressure by transmitting those forces from the snow fence or snow guard to the roof surface and through that roof to the roof mounting clips.

There are building codes for building roof system wind-uplift resistance on metal roofs but there are not building codes that describe the "shear strength" resistance for the fasteners used to secure metal roof panels to the roof deck.

Failures in the mounting system for snow retention devices can occur if the snow retention system is not adequately secured to the building structure itself. Damage to the roof or roof covering can also occur if the total snow and ice load bends or breaks the roof covering (such as a standing seam metal roof).

If the total load causes the roof mounting clips beneath the metal roof to shear. In our OPINION given the total number of clips used to secure the length of a standing seam metal roof panel to the roof deck below, the chances of shearing of all of these roof mounting clip screws, properly screwed to a sound plywood or even OSB roof deck should be minimal.

However it is plausible that high snow and ice loading near the roof edge, imposed against snow guards or a snow fence in that location, could provide a bending force that pulls fasteners out of the roof deck, bending or damaging the roof, and sending snow guards and snow and ice to the ground below.

Adhesive failures are reported by Galow, Anderson, and others as a common snow retention system failure for glued-on snow guards on metal roofs, as we discussed above. [15][20]

Structural damage can occur if the snow retention system is not properly located on the roof. See SNOW GUARD SPACING & PATTERN for an explanation of ice dam loading on roof extensions.

The load on snow guards as well as the relationship of snow loading on roofs and the use of snow guard was investigated by Tobiasson (1996) et als. who concluded that improved design guidelines, standards and performance criteria are needed for snow guards on metal roofs.

There are however recommendations for snow retention system installation from the manufacturers of these systems. See SNOW GUARDS on METAL ROOFS for examples.

References for Snow Guards, Installation Methods, Standards

Metal roof with no snow guards, Poughkeepsie, NY (C) Daniel Friedman

Snow Guard & Snow Brake Articles

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SNOW GUARD BUILDING CODES? at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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