01 May 1999
(1) Wall Flashing with Wall Parallel to Panel Seams. Parapets that parallel the standing seams
require floating flashings. The base component of such flashing is anchored to the metal panel and
moves with it. A counterflashing anchored to the wall covers the base flashing and provides additional
protection (figure 9-7).
(2) Wall Flashing with Wall Perpendicular to Roof Panels (Headwall Transition). Roof to head
wall transitions must have a gap between the panel and wall to allow for thermal movement. The gap is
covered with a flexible flashing membrane for watertight performance or covered by a two piece metal
wall flashing system (figure 9-8).
(3) Sealants. Sealants are used in all waterproof seams. Factory sealant is installed into the
female seam of factory formed panels. Sealant in tape form is used at endlaps and other places specified
by the manufacturer. Pumpable sealant (caulk) is used to supplement the other types. In general, butyl-
based materials are preferred because they tolerate finishing oil that may be present on the panels or coil
stock and they retain their adhesive properties for many years when protected from the weather.
(a) Additional field applied sealants are necessary in hydrostatic side seam design where
attachment clips are located to restore continuity of the seam sealant.
(b) Refer to the weather tightness requirements of ASTM E1514.
(4) Fasteners. Many different fasteners are used in metal roof systems. Coarse threads (Type
A) are best for joining two thin sheets of metal together (stitching), while finer threads for lower tapping
torque are used when engaging thicker materials. The elastomeric washers provided as part of the
integral head serve a waterproofing function and should not be overtorqued. For color metal panels
matching colored fastener heads are available.
(5) Clips. Clips are designed for each proprietary type of panel. For SSSMR, CEGS 07416
stipulates: "clips shall be made from multiple pieces with the allowance for the total thermal movement
required to take place within the clip. Single piece clips may be acceptable when the manufacturer can
substantiate that the system can accommodate the thermal cyclic movement under sustained live or
snow loads." Typically, clips are designed to accommodate thermal movement on the order of 25 mm (1
in.) to 38 mm (1.5 in.).
(6) Accessories. Accessories include prefabricated curbs with flanges matching the rib and
seam configuration of the panel and roof jacks i.e., pipe penetrations, which also match the panels.
Drainage, Valley and Intersection Details.
(1) Water Flow. Water must run parallel to all standing seams. At down-slope curbs and
penetrations that block water flow, the standing seams must be truncated short of the curb and a diverter
installed so that water can move around the penetration.
(2) Gutters. Internal gutters can be problematic especially in cold regions. If roof geometry
necessitates internal gutters other kinds of roofing should be considered.
9-3. DESIGN CONSIDERATIONS AND ALERTS. Refer to specific design details for each metal panel
system being considered. In addition, refer to the NRCA Roofing and Waterproofing Manual, Volume 2
and the SMACNA Manual for Guide Details. Caution--Most SMACNA details are watershedding and
should not be used in watertight applications.