[JRTJH]

Delamination doesn't occur "because the FILON got wet last night. It occurs when the sun beats against the trailer side, causing the moisture inside the wall to turn to steam. It's the steam that expands, causing the fiberglass strands to separate and lose adhesion. On the sidewall of your trailer is a "complex sidewall system" (not just a sheet of fiberglass). It starts with the exterior FILON (complete with waterproof coating) which is backed by a 1/8" luan (imported hardwood plywood) backing. That is glued to a rigid foam core that is laid to fill the spaces between the aluminum frame channels. Next is another luan ply with vinyl coating which forms the interior wall. Damage may show up in a few days, it may not show up until the trailer is exposed to extremely hot sunlight for a prolonged time or it may not show up until the moisture "freezes next winter" and damages the substructure. It may take weeks, months, years to appear, but it won't reveal increasing damage "in a couple hours". So, not seeing a "growing delamination this morning" is not going to be a sign of "it's not a problem"....

All of that structure is subject to moisture intrusion which can cause water damage. Exactly where the steam will produce the separation or the failure of the adhesive is anybody's best guess. Typically it starts with "rotting of the luan" which then gives away with no substrate to support the glue that holds the FILON to the underlayers of aluminum and foam.

Also, you "could have" delamination occurring "inside the FILON" which breaks down the actual fiberglass, forcing it to separate from itself.

So, "delamination" is really one of multiple failures. How the moisture will "attack" your sidewall will depend on which component is the "weakest link" in the sidewall structure. It really takes more than a quick diagnosis of an unseen problem to make a proper assessment of just "which kind of delamination" you have going on. It could be as simple as steam being produced under the coating and not affecting the actual fiberglass sheeting or it could be total failure of the luan under the fiberglass. Someone familiar with RV sidewall structure and failure needs to take a look and make that determination. It's not always the same problem.