I'm working on a house with new posi joists at 600mm centers. We will be plasterboarding in the next few weeks. Would a 12.5mm sheet be ok or will it have to be 15mm? There are no noggins and the boards will be foil backed.
i started a site today (timber frame).the agent has insisted that 600 centres with no noggins on ceilings taking a 12.5mm board is ok. This is to be skimming also. I mentioned this to him a few weeks back although he reckons it's fine Your thoughts please Cheers
The board manufacturers will say 12.5 is ok, but there is still quite a bit of flex if there is no noggin. 15mm would be better to use. Some pozi-joist are 150mm so in essence, the unsupported span is only 450mm