It Fails at the Fixings and the Details

A metal panel in good condition can be held down by fasteners that have corroded, backed out or lost their seals. On an exposed coastal roof the fixings are the shortest-lived element, and a roof that looks sound from the ground can be inadequately attached.

There is a second failure mode specific to exposed-fastener systems. The screws carry rubber or neoprene washers that seal the penetration, and those degrade in ultraviolet long before the panel does. A roof can be perfectly sound metal held down by several thousand fasteners whose seals have hardened and cracked.

Start at the penetrations and the terminations — vents, pipe boots, ridge, eaves and any point where the panel is cut. Then look at the fasteners across the field, particularly on the most exposed elevation, for backing out, corrosion or degraded washers.

Then look for staining running down from any fixing, which indicates water tracking through. On a coastal roof it is also worth looking at where different metals meet, because that junction corrodes faster than either metal does alone.

1. 01Assess fixings as well as panels.
2. 02Repair or replace flashings and penetrations properly.
3. 03Address corrosion rather than coating over it.
4. 04Confirm attachment meets current requirements where replacing.
5. 05Document the condition for you and your insurer.

Look at where dissimilar metals meet. Coastal corrosion concentrates at those junctions and at cut edges, and it is invisible from the ground while the panels themselves still look perfectly good.

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