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47.5 MB - The Whole Building Design Guide

47.5 MB - The Whole Building Design Guide

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specifying a secondary membrane. <strong>The</strong> copper roof blew offthe hospital’s intensive care unit (ICU). Patients and staff werefrightened by the loud noise generated by the metal panels asthey banged around during the hurricane. Fortunately therewas a very robust underlayment (a built-up membrane) thatremained in place. Since only minor leakage occurred, theICU continued to function.Figure 3-86:Because this roof systemincorporated a secondarymembrane, the ICUwas not evacuated afterthe copper roof blewoff. Hurricane Andrew(Florida, 1992)m For an SPF roof system over a concrete deck, where the basicwind speed is less than 130 mph, it is recommended thatthe foam be a minimum of 3 inches thick to avoid missilepenetration through the entire layer of foam. Where thespeed is greater than 130 mph, a 4-inch minimum thickness isrecommended. It is also recommended that the SPF be coated,rather than protected with an aggregate surfacing.m For a PMR, it is recommended that pavers weighing a minimumof 22 psf be specified. In addition, base flashings shouldbe protected with metal (such as shown in Figure 3-93) toprovide debris protection. Parapets with a 3 foot minimumheight (or higher if so indicated by ANSI/SPRI RP-4, 2002)are recommended at roof edges. This manual recommendsthat PMRs not be used for critical facilities in hurricane-proneregions where the basic wind speed exceeds 130 mph.3-108 MAKING CRITICAL FACILITIES SAFE FROM High Wind

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