Fiberglass decks are not completely maintenance free. The gel coat should be reaplied at certain intervals.In some cases, I've seen these decks pull apart at the seams of the underlayment. If you do a sleeper deck, I would make it modular so that the deck may be serviced.:thumbsup:Can a composite or wood deck be installed over an existing fiberglass deck over living space. I know some kind of sleepers must be installed and roof membrane could be involed.