Repairing a delaminating exterior panel on a motor home requires some care and precision. You must be careful to avoid damaging the exterior panel, exacerbating the damage already present. Delamination is caused by one of two things. One is that the panel was not properly glued at the factory. If you own a motor home still under warranty that is delaminating, return it to the dealership for a proper repair. The other cause is a water leak that breaks down the glue between the fiberglass panel and the wood underneath.
Locate the source of the delamination. It will appear as a small hole or crack between the wood substrate of the motor home and the fiberglass outer skin.
Cut the delaminated panel away using the utility knife and remove it. Scrape the glue off of the back of the panel using a scraper.
Run a short bead of construction adhesive across the top of the delaminating panel where you determined the water leak was occurring. Even though you ran a full bead around the repair area previously, this will doubly ensure that future leaks are prevented. It is not necessary to apply construction adhesive to any other area of the panel once it has been glued in place. Allow the glue to dry according to the glue manufacturer's specifications.
Buff the area of the repair with a rag and automotive polishing compound to remove traces of the repair. Reinstall the surrounding trim.