Steep-slope metal roof systems, also called architectural metal
panel roof systems, are one of the fastest-growing segments of the
roofing industry. These systems are used in commercial and
residential applications and require installation over a solid
substrate, such as plywood, and use of an underlayment. Although
underlayment is used as a secondary protection against moisture
infiltration, proper flashing details are necessary to prevent
moisture from initially bypassing a steep-slope metal panel roof
Detail A-MTL-4 provides multiple lines of defense against
moisture infiltration. The first line is the "Z" closure, which is
set in continuous sealant (either a bead or tape); this includes
sealing the vertical legs of the "Z" closure to the panel seams.
Mechanical fasteners generally are used to secure the closure to
the panel; depending on the metal type, soldering the "Z" closure
to the panel also is acceptable.
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