Figure 1 Front elevation. Figure 2 Rear elevation with two wings, each with gambrel roofs intersecting the main roof, but at a lower level.

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1 A private school in a picturesque New England town is the setting for our first case study in snow retention. This significant building (Figure 1), on the campus of a prestigious private school, houses the offices of the president, as well as the admissions office, where all campus tours for prospective students start and end. The building also serves as a backdrop for annual commencement ceremonies. As a result, it receives a great deal of scrutiny, and when Figure 1 Front elevation. Figure 2 Rear elevation with two wings, each with gambrel roofs intersecting the main roof, but at a lower level. 34 INTERFACE O CTOBER 2011

2 Figure 3 Roof plan showing rear wings and frontelevation dormers. the 75-year-old slate roof and flashings were in need of replacement due, in large part, to damage at valleys and eaves from sliding snow it was a key requirement that the new roof design include snow management to prevent the premature demise of the new slate roof. The building has a clas sic gambrel roof shape; however, it also has two wings at the rear elevation that are perpendicular to the main portion of the building and create a complex pattern of ridges, valleys, and eaves. This is in addition to the front elevation with 14 dormers that concentrate sliding snow to narrow chutes, which have, in the past, cascaded snow off the building to the ground below (Figures 2 and 3). Damage to the slate at the complex valleys at the rear elevation caused significant damage to the hung half-round gutter at the eave, as well as to the slates near the valley (Figures 4 and 5). Snow retention was included as part of the reroofing design. The design was the result of a review of code consultation with snow guard manufacturers and good roofing practice, or Figure 5 Valley and slate repair/replacement at rear elevation. Figure 4 Valley at rear of building. O CTOBER 2011 I NTERFACE 35

3 Figure 6 Snow retention layout plan. Figure 7 Closed entrance due to falling snow. what we call common sense. The areas of greatest concern were readily apparent; all one had to do was look for damaged roof components or dead landscaping due to snow impact. The design of the snow retention was based on just that retaining snow where it typically falls. This was done with pad-style snow guards, which must be in stalled on the entire roof area, not just three rows at the eave. The density of pad-style snow guards was determined by expected snow loads, building framing limitations, and roof slope/configuration. These cal culations are beyond the scope of this profile; however, they are an interesting topic in and of themselves. Due to cost considerations, it was not feasible to install pads throughout the entire roof area, so it was decided to economize and install pipe-style snow fences at many areas. The pipestyle snow fence does not retain the snow where it falls; rather, it acts to stop a snow slide after it has started Figure 8 Ice buildup at gutter. Figure 9 Potential snow slide from gutter to building entrance below. 36 INTERFACE O CTOBER 2011

4 and prevents the snow from leaving the roof. In addition to the pipes, ice screens made from heavy-gauge, expanded stainless steel lath were installed to prevent large pieces of snow or ice from sliding through or under the pipes. The big-picture concept for the snow retention of this roof was to hold the snow where it fell in most areas and to stop any slides in areas that could cause damage to people or roofing, should they occur. To do this, Wiss, Janney, Elstner (WJE) installed two rows of pipe-style snow fences one at the eave and a second at the change in slope of the gambrel roof. These devices would stop sliding snow on the main portions of the roof from cascading to lower roof areas and ultimately to the ground below. At the steep portions of the gambrel roof, a dense pattern of pad-style snow guards was installed to prevent any significant amounts of snow from beginning to slide along the roof surface. Additional locations of pipe-style snow fences were installed at the valleys of the rear wings as an added precaution in the event a slide did occur, overwhelming the upper snow fences. A bid alternate that was deemed unnecessary was also designed and consisted of a sparse pattern of pad-style snow guards at the contributing area above the critical valleys of the two gambrel wings at the rear. The Snow Retention Layout Plan included in the bidding document is shown in Figure 6. The snow retention system was installed in 2009 as part of the general re roof of the building; and during the extreme winter of , it was reported that not a single slide of snow fell from the roof. Additionally, no hung gutters at the eave were damaged or deformed, and not a single slate slid from the roof. Some may say that the design was conservative, but when the costs of installing the components during the roof replacement are compared to the costs of annual repair to the difficult-toreach hung gutters, damage to painted wood trim, and damage to the slate roof and copper valleys, it was determined that the snow retention assembly has almost paid for itself in the last two years. Our second case study is that of a Gothic-style university in New England. The facilities staff is plagued with annual snow and ice slides from the steeply sloped slate roofs on the campus buildings. Past efforts to address the problem with single rows of pipe-style snow guards above doorways have proved ineffective (Figures 7, 8, and 9). O CTOBER 2011 I NTERFACE 37

5 Figure 11 Snow Guard Layout Plan. Figure 10 Damage at gutter from ice and snow slides. In addition to the safety concerns related to this condition, extensive repairs are required each spring to address damage at gutters caused by the snow and ice slides (Figure 10). During the winter of 2011, the university contacted WJE to request an investigation and development of a design to address the problem of the sliding ice and snow. Following a field survey, a design was developed incorporating the existing pipe-style snow guards, new pipe-style snow guards, ice screens, and pad-style snow guards. Above sidewalks and doorways, the proposed system includes a row of pipe-style snow guards with ice screens along the eaves with another row of pipe-style guards, without ice screens, located at 40% up the roof slope. Additionally, retrofit pad-style snow guards at 18 pads per square are located across the field of the roof slope. At areas away from pedestrian walkways, only pad-style snow guards are used. Due to limited funding, the snow guards were only to be installed at those locations most affected by the ice and snow slides. The Snow Guard Layout Plan included in the bidding document is shown in Figure 11. Paul C. Lanteri,AIA Paul C. Lanteri, AIA, is an associate principal with Wiss, Janney, Elstner Associates, Inc. in Shelton, CT. He has a bachelor of architecture degree from Illinois Institute of Technology and is a member of the American Institute of Architects. His experience includes both the design of new structures and roof systems, as well as the investigation and resolution of water infiltration problems and the restoration of roofing, façades, and windows at a variety of commercial, public, institutional, and historic structures. Remo R. Capolino, RRC, PE Remo R. Capolino, RRC, PE, grew up in a family-owned specialty roofing and sheet metal contracting business and graduated from the University of Connecticut with a bachelor s degree in civil engineering. After more than 15 years in contracting and leadership roles with the Association of General Con tractors (AGC), Northeast Roofing Contractors Associa tion (NERCA), and the National Roofing Contractors Associ a tion (NRCA), he turned to consulting. Capolino has lent his expertise in copper, zinc, slate, and other specialty roofing assemblies on a number of internationally recognized projects. He is a member of RCI and its Interface peer review board. 38 INTERFACE O CTOBER 2011