01 May 1999
polyester mat or butyl tape over the hole, followed by coating. Others involve oversized weather sealing
washers and fasteners.
(3) Differential Movement at Ridge Covers, Side Wall or End Wall Conditions. Differential
movement at ridge covers, side wall or end wall conditions may fatigue fastenings. Reflashing with
flexible membrane under the metal flashing may be needed.
(4) Endlap Leakage. Endlap leakage may be caused by a gap in the sealant within the lap. Top
coating with reinforcement provides only temporary protection. The lap may have to be disassembled
(5) Rooftop Penetrations. Rooftop penetrations, especially those installed after completion of the
roof membrane, may be incorrectly installed. Finished installations must accommodate thermal
movement of the panel. Flexible boots or proper curbs are needed to accommodate this movement.
(6) Replacement of Panels. Replacement of installed panels can be very difficult, especially
those which are machine seamed.
(7) Replacement of Fasteners. If fasteners have backed out or the washers have failed,
replacement of fasteners is appropriate. If fasteners have stripped the threads in the underlying metal,
replace with larger diameter fasteners.
(8) Suitability in Reroofing Applications. Structural metal roofing systems can sometimes be
used to replace or recover poorly draining membrane roofs. On relatively narrow buildings a
watershedding system and attic can be created by applying elevated lightweight structural supports
through the old membrane into the roof deck or structural members below.
Repairs: Emergency, Temporary, and Permanent
(1) Emergency repairs. Emergency repairs are sometimes done with duct tape, asphalt mastic
or butyl tape with foil facing.
(2) Temporary repairs. A temporary repair would be to embed a piece of sheet metal in butyl
sealant, screwed into the metal panel. The life of such a temporary repair will not match that of the rest of
(3) Permanent repairs. A permanent repair would be to install identical metal with corrosion
resistant fasteners embedded in the proper sealant, or if the damage is extensive enough, to replace the
d. Repair Work by User. Exposed sealant applied to laps, flashings, etc., that are suspected of
leakage is not durable. The butyl sealants that are installed between metal panels are extremely durable
because they are protected from sun exposure and dirt pickup. Recoating of metal panels is similar to
painting metal in general. However, flexible membranes are sometimes installed over fasteners, laps,
and penetration joints prior to coating.
e. Maintenance Checklists.
(1) Membrane. Inspect panels and seams for deformation damage. Use feeler gauge to
determine if sealant is present under endlaps on wet side of fasteners (figure 9-11). Look for corrosion
caused by the presence of ferrous materials, copper salts, or chemical aerosols.