Plasterboard type for ceiling?

[Donkmeister]

I need to reboard my upstairs ceilings.

100 years ago my house was built with lathe and plaster ceilings, and at some point in the past some of the upstairs ceilings have had damaged plaster removed and then foilbacked plasterboard affixed over the lathes. Unfortunately due to a presumed lack of joint taping these newer ceilings are now shot so I plan to pull down the boards, reboard, then get a spread in to tape and skim.

I have a well-ventilated loft, with no water tanks and no condensation issues. 8-12" of glass wool insulation over the whole loft. From what I've seen on previous houses standard 9.5mm plasterboard is fine for an upstairs ceiling, underneath a loft.

But, understanding that the previous owners were cheapskates who would cut any corner to save a few quid, I am wondering if there would be any reason to the foilbacked plasterboard.

Should foilbacked plasterboard be used on an upstairs ceiling?

 

[PrenticeBoyofDerry]

Foil backed boards are used when a vapour check barrier is required, so if you have insulation above board it is wise to provide a vapour check, whether this be part of the board or supplementary to it, that is your choice. I would always recommend using at least 12.5mm boards for ceilings.

 

[tomfe]

You have a vapor permeable insulation above, it would be different if it was PIR/EPS etc.
Foil back is a bit of a con IMO, you don't foil the joints behind the board or any penetrations like reassessed lights so what's the point. Gypsum plaster is a fairly good vcl. So if you really want to put something in use some plastic sheeting.
I'd use 12.5mm for fire safety.

 

[Doggit]

I'd just leave the existing boards where they are, and overboard them. They're not doing any harm, so why take them down.

 

[Donkmeister]

Thanks all.

I've just been up in the loft and was surprised to see how much condensation has formed up there since I exposed the lathes in one area, it's literally dripping off the sarking. Never had that before, even when I had a cistern and F&E tank up there. So, I will definitely install a vapour barrier as part of the reboarding.

I'll go with the 12.5mm as you recommend, I hadn't considered the fire protection aspect.

 

[PrenticeBoyofDerry]

I'll go with the 12.5mm as you recommend, I hadn't considered the fire protection aspect.

12.5 vs 9.5 with regards to fire integrity is going to be negligible. 12.5mm will not sag like 9.5 will

 

[delberto]

Creating a new whopping great hole from a warm humid living space through into a very cold and poorly ventilated loft space will obviously cause lots of condensation.
Overtacking the existing plasterboard with 12.5mm plasterboard and wet plastering it will give you good fire resistance and sound proofing and goes a long way towards airtightness. Install some ventilation in the loft if you are concerned with condensation. There are lots of debates about the use of vapour Barriers in various climates so I don't really have a firm opinion on those, but the regs do require one so it might indemnify uou (somewhat) if you ever need to make an insurance claim for damp in the loft.

 

[PrenticeBoyofDerry]

delete post