The old adage, "simpler is better," is especially apropos to building in snow country. Pure geometric roof forms, including flat, shed, and simple gables, almost always function as intended, thanks to the predictability of snow loading, sliding, waterproofing, and meltwater drainage on these roof types (Figure 11). Snow and cold country design solutions for these simple geometric roofs are easier to achieve, more economical to build, and subject to fewer construction errors than solutions for more complex roof geometries. Unfortunately, some clients insist on complexity as they associate it with traditional alpine design.
Snow and cold–related design problems tend to escalate when sloping roof dormers, valleys, downslope roof projections, chimneys, and complex roof geometries are used in the name of architectural aesthetics and style. In most cases, these complex forms reduce a roof's chances of functioning properly and mitigating problems through design and construction is often challenging (Figure 12).
Complex roof designs can significantly change the environmental patterns that act on the roof form. For example, wind deflected off complex roof planes will cause snow drifting. Shadow patterns cause snow to melt unevenly. And complex roof shapes channel snow, causing it to slide or creep down valleys and between dormers, where it can jam and create overload and leak problems. In cases of overloading, a high roof may avalanche onto a lower roof, balcony, or entry (e.g. broken deck rails are common in snow country). To use a musical metaphor, a simple roof has a low-key melodic tune; a roof shaped by complex geometry can erupt into a cacophony of snow and cold problems.
There's always an exception: Complex roof forms can work well when the roof is designed to retain snow. The intent in this case is to mitigate snow creep and sliding once the snow blankets the roof. Any melting should be caused only by the weather and, when that melting occurs, the meltwater should not allow the snow blanket to move. To prevent ice dams and icicles, the meltwater runoff should be controlled and not allowed to refreeze (Figure 13).
