Snow Build-Over On Pergolas, Trellises & Mechanically Louvered Roofs (Cornice)

snow buildup on trellis example

Beware of Snow Buildup On Open Roofs

An important and frequently overlooked requirement for checking snow loads on open roof systems

snow buildup on trellis example

such as pergolas, trellises, and mechanically louvered roofs is the snow ‘buildover’ effect.  This occurs when the snow accumulates on open patio roof components to the point where it builds ‘up and over’, touching the snow on the adjacent roof component.

ASCE 7 section 7.13.3 states that when the spacing between open components is less than the buildup height of the snow, an additional uniform cornice load shall be applied to the space in between.  This is illustrated on ASCE figure 7-13 shown below, along with some illustrative examples.

Engineers must consider this loading when evaluating the design capacity of open roof patio enclosures, as well as all uplift, gravity, and lateral forces, snow drift, seismic, and dead load considerations.  The engineers at Engineering Express are experts in this field and frequently design open patio structures for review by project engineers, architects, and plan reviewers across the US  Chat With Us to discuss your need or request a quote on your next project.

Figure 13.3-3 from ASCE 7 Illustrating snow buildup on open roofs

snow buildup on trellis example         

Last Update: September 26, 2022  

September 26, 2022  Codes & Standards  
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