Originally Posted by carlcaudill
I understand the roof material on my 2006 Forester is fiber glass. I have a soft spot under the fiber glass on the front right where the roof meets the front cap from a previous leak. Every one has told me it would be to expensive to repair the soft spot so I should keep a eye on it be leave it alone. Has anyone ever tried to inject some form of floor leveler under the fiber glass to strengthen the roof in that area.
From my involvement with fiberglass boats:
If the roof is indeed fiberglass there is a core material underneath the thin fiberglass to provide rigidity. There should also be a layer of fiberglass on the underside of the core. Commonly used core materials include balsa, foam, and (unlikely in an RV where light weight is critical) plywood. The panel's structural integrity relies on the core being intact and the fiberglass-to-core bond remaining sound. Localized failure of either causes "soft" spots. Typically, the bond failure or core rot will spread with time and cause failure of the entire panel.
If a portion of the core has been infiltrated by water, ideally that section of core should be replaced, and the fiberglass skins (both) repaired with new fiberglass. It's not difficult work, but it is time consuming and messy. Getting gel coat color to match exactly is very difficult - you are often better off painting the entire roof with a polyurethane or epoxy paint when done.
I have seen attempts to inject "Git Rot" or similar epoxy mixtures into the failed core section - but never with long term success. The injections never get all the core where the water damage has occurred. And you still need to seal the injection holes, and pray that the fiberglass-to-core bond is still sound everywhere.
just my experiences with boat repairs