Why do the fixings fail before the panels?
A fixing is the part that moves with the wind and the heat, and it is also the part that water finds first. A washer that has aged loses its seal, and a screw that has backed out lets the panel rattle and then lift.
Metal expands in the sun and contracts at night, and the fixings take that movement every day. A screw that is driven too hard crushes its washer, and one driven too lightly does not hold. Over years the washer perishes and the screw works loose, and the panel begins to move at each fixing.
The technician therefore tests the fixings by hand along every run. The fixing is the cheapest part to renew, and renewing it early stops the panel from being damaged by its own movement.
How is a dented panel judged?
A dented panel is judged by whether the dent has cracked the coating, split the seam or broken the rib. A dent that has only bent the rib can often be straightened; a crack or a split is replaced.
A dent in a corrugated panel is often visible from the ground as a shadow across the ribs. The technician checks whether the coating has cracked, since a cracked coating lets rust begin at the bend. A crack along a rib is a sign the metal has fatigued and the panel should be replaced.
Where a panel is replaced, the new piece is chosen for the same profile and gauge. A different profile will not lap over the neighboring panels, and the joint is then a route for water.
Why are the penetrations and trim checked with the panels?
The penetrations for vents, pipes and lights and the trim at the ridge and eave are where a metal roof most often leaks. They are checked in the same visit so the water is not directed around one repair into another.
A pipe that comes through a metal roof is sealed with a boot or a flashing that lies over the panel. A boot that has split or a sealant that has cracked lets water run down the pipe into the framing. The boot is replaced, and the sealant is renewed where it will bond.
The ridge cap and the eave trim are fixed to the panels, and a trim that has lifted lets wind-driven rain under the panel. Each trim piece is re-fixed and sealed, and the lap is checked against the panel below.
What should a rural owner check between visits?
A rural owner checks the fixings and the trim from the ground each season, looks for light in the attic and walks the perimeter after a windy day to see whether any panel has moved.
Panels that have lifted at the eave, a ridge cap that has shifted or a fixing that shows a crater of rust are visible from the ground with binoculars or a camera. Photographs from the same spot make the change easy to see.
Light in the attic is the most important sign. A pinprick of daylight on a dark day means a fixing or a seam is open, and the technician should be called to trace it before the next storm.
