Bulge in exterior fiberglass...

WoodGlue wrote:
You have wet Luaun in the walls. Luaun is a wooden board used in walls and when it gets wet, it expands and contracts, helping to cause delamination. I'd say your best bet is to let the thing dry out completely before resealing anything (if you're able to). You may have mold and mildew on the inside of the walls as well, as wood and trapped moisture usually is a recipe for mold & mildew.

It looks like maybe you should hire a professional to do the repair work as it looks severe.

That's why composite substrates like Azdel or Compositek are such lifesavers if you do develop a leak. Azdel will not absorb water, and is mold and mildew proof. Azdel coupled with 2" block foam insulation and pinch rolled fiberglass (like Lamilux) is almost bulletproof. Only a couple of RV manufactures employ this technique.

Good luck to you,

WoodGlue

There are no absolutes about the materials in the OP's damaged area and the propagation of mold and mildew. Adzel used in a composite wall structure is not immune to mold should the correct temperature and humidity be reached.

The best tactic the OP could use is to seal that opening and, therefore, lower the humidty. That would lower the potential for any mold in the walls and further delamination The wall structure will dry out because it is not hermetically sealed.