Out side wall of a class c is coming apart.

I agree that a picture would be a help.

If you mean that the outer skin is separating from the underlying structure and looks sort of bubbled out, it's a probable sign of water damage to the area (and quite possibly surrounding areas). The cabover section of class C motorhomes is rather frequently a site of water leaks. Repairs are possible, but often require a lot of time and effort (or, alternately, a lot of money for someone else's time and effort).

Picture is worth a thousand words.
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If the outer skin is coming loose then that's a classic sign of delamination - usually associated with prolong leak where moisture has degraded interior support system and related glue. Often expensive fix that requires removal of exterior skin, repair of interior damage etc .... picture might help.

Could you be more specific? What Brand - is it a slide - does it have glass, or metal walls - is it on the "road side" or the door entry side. Can you send a picture or two.

bbt