plasterboard......

one other thing as well....my tiles (11 of them) have still not been put on my roof.... they sit just above the garage.....the plaster board has gone up and now the last few days it has rained a fair bit....almost as much as Melbourne:p but four of the sheets now have water stains..... what I want to know is will this wharp.... should I make them replace it????? I did mention it to them and they told me it was water resistant as they used the same plaster as the eaves

plasterboard on the eaves? sounds odd but maybe they do it different over there.

using a wet area plasterboard on a ceiling sounds odd too.
you sure it's plasterboard in the garage and not hardiflex or villaboard(fibro)

give it the finger test, if you can poke a hole though it it's buggered :)

in any case it's a poor effort on their part to have a swimming pool on top of the ceiling!!!

Doubt it's plaster. Probably cement sheet. Water wont hurt it.