My ceiling needs some tlc - cover up or replace?

Hi
My ceiling in my back bedroom used to be covered with badly fitting polystyrene tiles. Underneath the ceiling tiles I find ceiling wall paper. Underneath a few of the loose tiles I found what looked like black mold, although the ceiling didnt feel damp to the touch.
Now that the ceiling is bare I can see the reason for the polystyrene tiles. The ceiling is quite bowed, but I dont have a problem with this as the house was built in 1900 so most ceilings this age probably bow to some extent. What is a problem is the part with the black mold is quite badly bowed and cracked. Each part of the ceiling where the cracks are will bend gently upwards independently of the rest of the ceiling, so the crack must go right through the ceiling board.
I have hoovered teh black stuff off the ceiling and it looks quite a bit better.
Can I get some pollyfiller that will fill teh cracks on the ceiling - or will this just crack again and fall out?
The room isnt that big - big enough for an adult single bed and a small table & storage cupboard. Would it be expensive to have the ceiling replaced? Are there certain materials that shoudl be used when replacing the ceiling? I seem to remember people mentioning two different thicknesses of ceiling board and only the thicker sort is any good whereas the thinner board will just bow.
Thanks for any help
S.
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none wrote:

Just pull it down and replace it.

Not particularly.

Plasterboard, either 9.5 or 12mm will do. Then get it skimmed - it'll take a good plasterer a couple of hours to skim a ceiling that size.
--
Grunff

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Grunff wrote:

Hmmm. Actually I'd suggest plasterboarding over and skimming. You're not going to lose much height in the room (!) and it's much less mess-making. IMHO, YMMV etc...
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mark snipped-for-privacy@pobox.com wrote:

Nasty, dirty bodge. The PB will never sit properly over the deformed, non-flat lath and plaster. Taking down l+p is no fun, but it's the right way.
--
Grunff

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and makes sure that there isn't a hidden cause for the mildew eg. leaks or water ingress, dooo it.
--
fred
Plusnet - I hope you like vanilla
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..but investigate the reason for the leak first.
sponix
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