hi guys,am i right in thinking that i can just board over an existing ceiling,screwing through it,then into the joists?whats the best thickness of board to do this 95 or 125mm?current ceilings slightly off and was gonna level new boards with a bit of bonding where needed.its too "off" for just a reskim.i was gonna rip old one down,but theres soo much crap and dodgy insulation above it in the loft,im tryin to avoid it.any advice much appreciated..