1 June 1998
exterior of the building envelope causing far less problems. The SSSMR system is capable of
incorporating a waterproof membrane on top of the substrate (metal decking), the same as for a
nonstructural metal roofing system. Installation of mechanical, electrical, or other roof-mounted
equipment should be avoided, but if it is necessary, the equipment should be supported by
factory-fabricated, fully welded, insulated metal roof curbs, finished to match roof panels in color
and type of finish (PVF), free to float with roof panels, and supported underneath with structural
framing with no connection between the roof curb and structural supports. Roof access and
metal walkways should be properly designed and provided when routine maintenance of roof-
mounted equipment is required. Also included, as part of the SSSMR system, are the ridge,
gable trim, eave trim, gutters, scuppers, fascia, soffit, and flashings necessary to produce a
complete roof system. SSSMR systems commonly used are shown in figure 1.
c. Nonstructural metal roofing. Sometimes called Architectural Metal Roofing, this system of
metal roof panels is attached by concealed anchor clips to a continuous solid support substrate.
Panels carry no structural loads and are not capable of spanning between structural supports
without benefit of substrate materials such as wood, metal, or concrete decks. Applied snow,
dead, live, concentrated, and wind loads are resisted by the support substrate. Panel inward and
outward loads are transferred to and resisted by the substrate material. The anchor clips hold
panels in place and resist upward panel pressure. Loads applied to the substrate material are
transferred into the building structural system. The panels serve primarily as an aesthetic water
shedding material covering like shingles. Items such as the ridge, gable and eave trim,
scuppers, fascia, soffit, and flashings are available from manufacturers, but are not normally
considered part of the system.
d. Corrugated (through-fastened) Metal Roofing. This type consists of lapped, exposed,
through-fastened metal roofing (in various shapes: corrugated, R-panel, M-panel, etc.) made of
cold-formed metal roof panels that have lapped end and side seams. These panels are normally
attached directly to the metal structural framing system. While these systems are less expensive
than SSSMR systems or nonstructural SSMR systems, they are prone to leak over time due to
the thermal expansion and contraction of the panels. Leaks occur when the expansion and
contraction process elongates the fastener holes and loosens the fasteners which depend on a
gasketed neoprene or EPDM fastener for a seal. This type roofing should be used for
agricultural, industrial, warehouse, or utility metal buildings where a utilitarian look and
performance is acceptable. Do not use this roofing for buildings that require office, classroom, or
similar conditioned spaces. These lapped, exposed through-fastened metal roof panels span
between supports spaced 750 mm to 1,500 mm (2 ft.6 in. to 5 ft.0 in.) on center and resist all out
of plane applied loads and should be a minimum of 0.61 mm (0.024 in.) thick. Forces in the
plane of the roof are resisted by cross bracing.
5. BASIS FOR DESIGN.
a. General. Panels are available in copper, steel, or aluminum. Steel is generally the most
economical choice. Aluminum has applications in highly corrosive environments where steel is
inappropriate. These materials should not be specified as optional materials, but should be
specifically selected based on the requirements of the project.
b. Criteria. The roofing design will be in accordance with the following criteria.