plasterboarding ceiling- some advice

[andy1020]

Hi folks,
I see someone else posted about their ceiling recently who put 9.5mm board over old plasterwork.

I'm considering putting 9.5mm boards over old 12.5mm boards on the ceiling in my kitchen. (Old board damaged by a wood ceiling nailed up which I've taken down. Could be reapaired & plastered but i don't fancy plastering a ceiling...)

Questions:

1. What is better- nails or screws? I think screws will hold better seeing as I'm putting it up over old platerboard?

2. on the screws- is size 6 OK or too small. (They're long enough- 50mm)and is allowing the head of the screw to embed into the board OK? (ie- so that it's at least flush and I can skim over it for a smooth finish without having to skim the whole ceiling)

3. Should I really be taking the old board down? Really don't want to due to the mess..

4. Do I need to trim the wall plasterboard at the top of the walls and try to slide the ceiling board over it to support the edges, or will I get away with just making sure I have plentry nails/screws at the edges?


Also any other general advuice before I start later today?

Thanks.
Andy.

 

[noseall]

i would be inclined to overboard the old, if it were a large ceiling and i didn't want too much disruption to the walls below.

but, by removing the existing ceiling, you do have the benefit of knowing exactly where the joists are and are able to access any cables or pipes should you need to. you also have the opportunity to include some sound insulation too.

i only ever use 9.5mm boards if i'm marrying into existing 9.5mm boards or if the tolerance parameters dictate i have to.

screws would be best for overboarding. use 50mm drywall, bugle or trumpet heads.