26 September 2006
Panel edges must be of male and female interlocking design with a machine folded
(mechanically seamed) finishing of the seam. There can be no gap between any
surface of interlocking male and female seam portions. Finished seam configuration
may be either 90-degree, single fold (resembling an inverted "L") with horizontal
dimension of 16 mm (0.62 in.) minimum, or a 180-degree, double fold.
Each seam must have a pre-applied bead of non-curing, non-hardening
polyisobutylene-isoprene copolymer or terpolymer (butyl) to ensure complete
hydrostatic performance. Sealant may be a hot melt butyl formulation if applied at the
point of panel manufacture. Gas entrainment of sealant is permitted. The roll-forming
machine must apply sealant. Continuity of seal with field applications through all panel
termination points is critical. Silicone sealant is not allowed. Primary seals must always
be concealed within a joint. When secondary seals are used, they may be exposed
The minimum allowable slope is :12 for Military projects.
With specific approval, the Army will allow :12 for large new roofs and reroofing
whereas the Air Force and the Navy will only allow :12 for large reroofing projects.
Material and weather tightness warranties typically exclude slopes below :12. Care
must be taken to ensure that structural deflection and/or fabrication camber does not
result in slopes below the allowable.
Attach panels with concealed clips. Thermal expansion clips are to be of a two-piece
design, having a top portion that folds into the panel seam and a base that attaches to
the structure. The joining of base to top components must anticipate the full range of
thermal cycling of the panels, using panel temperature delta T of 93 degrees Celsius
(200 degrees Fahrenheit). Higher delta T may be necessary in cold climates when
using dark roof colors. Maximum frictional resistance between top and base
components must not exceed 2.25 kg (5 lbs.) in the finished, folded seam. When eave-
to-ridge in-plane dimensions are less than 7.6 m (25 ft.), fixed (one piece) clips may be
employed. Clips must be "wetted" to the male seam component with butyl sealant as
necessary to ensure complete hydrostatic performance of the joint and as required by
Panels must be rigidly fixed (pinned) to the building structure at a single point along
their length. Normally that point is at the panel's ridge or eave end. Such attachment
must be designed to resist all in-plane service loads including snow and other