01 May 1999
o.Gaps, Flashings, Joints, and Sealants. Each system has specific details for hip and ridge
closures. References include NRCA, SMACNA and Copper and Common Sense. Elastomeric sealants,
caulks and closure components should not be relied upon for roof integrity; these materials will not have
life expectancies consistent with these metals. Some sealants are incompatible with copper. Acid curing
silicones may be unacceptable. Verify compatibility with the manufacturer for sealant recommendations.
Endlaps must be designed for thermal movement.
p. Drainage, Valley and Intersection Details
(1) Drains and Gutters. Roof drainage systems are discussed in detail in Chapter 1 of the
SMACNA Architectural Sheet Metal Manual. Gutters are also discussed in detail in Copper and Common
Sense. Two distinct types are described:
(a) Built-in gutters may be installed level for strength. Maximum safe distance from any fixed
point such as outlets or downspouts depends upon cross section shape and thickness of the copper
used. See chart in Copper and Common Sense.
(b) Hung molded gutters should be 20 ounce copper with expansion joints not more than 48
ft apart, 24 ft from corners. Spike and ferrule method is not recommended.
(c) Roof gutters should be designed so the front edge of the gutter is lower than the back
and any overflow will spill over the front of the gutter. The elevation difference should be 1/12 of the
gutter width, 25 mm (1 inch) minimum.
(2) Sliding Snow. Snow guards are necessary on most steep metal roofs in cold climates
subjected to snow accumulation.
10-3. DESIGN CONSIDERATIONS.
a. Guide Details/Resources. Guide details are provided in the SMACNA Architectural Sheet Metal
Manual, the NRCA Metal Roofing Section of their Roofing and Waterproofing Manual, Copper and
Common Sense by Revere Corp., and the Copper Development Association Copper in Architecture.
b. Substrates. The surface to receive the metal roofing should be dry and smooth, free from
projecting nail heads or other obstructions. The underlayment should be No. 30 saturated roofing felt
(ASTM D226) lapped at least 50 mm (2 in.) and secured with copper, brass, or Series 300 stainless steel.
A layer of smooth building paper should be laid over the felt immediately preceding the application of the
c. Nailers. When decks other than plywood are used, it may be necessary to provide wood nailing
strips for securing cleats. The nailers are run perpendicular to the standing seams and spaced 300 mm
(12 in.) apart.
d. Pan Clearance. When standing and batten seam pans are used a minimum of 1.6 mm (1/16 in.)
space should be allowed between the base of adjacent pans.
e. Low-Slope Locking Strip. For slopes between 8% (1:12) and 25% (3:12) the transverse seam of
the upper panel is locked into a locking strip soldered to the lower pan. For steeper slopes (>25%) the
separate locking strip is not used (figure 10-2).
f. Military References/Guide Specifications. Refer to CEGS 07610-Copper Roofing.