Thickness of plasterboard for overboarding ceiling?

Hi there,

I've a couple of bedroom ceilings (with loft above) which are some kind of woodfibre boards.
They're reasonably flat, but a bit shabby, and not fireproof.
Joists are 400mm centres
We're planning to overboard with plasterboard, and then have them skimmed - am I right is saying we should go for 12mm, rather than being lazy cheapskates who put up 9mm, or does it not matter?

Cheers, Stephen

 

StephenStephen, good evening.

Best option will be 12. mm + skim.

Odd that the ceilings are "Cellotex" [the soft brown fibrous material?] that must have been a real cheap skate not to mention spread of fire?

Points to consider?? the Cellotex will burn, But?? can afford some thermal insulation [no a lot]

Consider removing the Cellotex and then re-boarding + skim then increase the loft insulation.

Down side to last is that there will be a load of old dirt, dust and general crap that will fall down when the Cellotex is being removed, plus any glass wool insulation will fall into the room messy to remove?

Ken

 

Yes - I did debate with myself about removing the old ceiling first, but as you say - it affords some insulation and would create a lot of extra mess and work to remove. I'll go with 12mm plasterboard

 

Cellotex is not wood fiber. More likely hard board or MDF. This might indicate a bad DIY or boddged job else where.
Just over board and skim.

 

If it's an older house it might well be Sundaela board (softboard) which was used extensively as an insulation/attic ceiling material in the 1920s to early 1950s and it's a brown fibrous material. I'd not describe hardboard that way. Sundaela was generally just nailed in place and painted. Record used to sell planes that used a sort of disposable razor blade cutter to chamfer the edges where the boards joined. It tends to swell and the wood fibres used in it's construction show when it gets a bit damp

 

Yes, softboard, that's the stuff, thank you