“One never can know enough about snow”
     - George Leigh Mallory, 1923

Rough-surfaced materials such as wood shakes, tiles, and composition shingles will hold snow on the roof in most instances (Figure 19). With multiple storms, however, the volume of snow can become quite large, and even a rough-surfaced roof will permit snow to creep downslope or even avalanche under some conditions. If that happens, the roofing material may be pulled off with the snow, especially if ice dams or icicles are present. If the design decision is to retain the snow on the roof, a snow retention system should be constructed to ensure that snow stays on the roof until natural melting removes it. The roof surface and snow arresters must be designed to withstand the glacial forces of the snow and ice. These forces are great and require special structural design.


Conclusion

Roof characteristics, including orientation, geometry, texture, temperature, and type, interact with one another in a multitude of variations. A thorough analysis of the site's environmental conditions and the use of a roof designed to meet the site's specific challenges can greatly reduce snow loading and ice dam problems.

While the roof is a major factor influencing snow and cold country design, it is not the only one. The design and selection of building enclosure elements, including walls, floors, and windows, are also of vital importance. Access to areas around the building can be important too. For example, if the design calls for dump zones, the fallen snow and ice may need to be removed after each storm, the designer may need to study the method of removing snow and ice as well as the space required for it. (Figure 20). Humidity and condensation are also major sources of interior damage and must be dealt with by proper application of vapor retarders.

Successful design in the snow country can be realized only when each ingredient in the frozen-country recipe is thoroughly understood and evaluated by those who design and build in this challenging domain.


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Figure 20
Figure 21