Advice on DPM and Plasterboard?

[TheBronster]

Hi guys,

I have a 1930s bungalow up the coast. It was originally weatherboard now covered with Tyrolean render which is being renewed. Due to downpipe and guttering problems (now fixed) it had developed bad damp and rot in the subfloor in one room. The entire floor has since been removed and has all been replaced with new joists bearers, t and g chipboard etc. The space between the floor joists will also be celotexed. New studs have also been sistered into the walls where necessary. I am confident that all the damp issues have now been resolved but want to know the best methodology for refinishing the wallls. I was going to celotex with 50 mm then use foil backed plasterboard but do you think I also need a polyethylene DPM over the studs before the foil backed plasterboard or not? Should I ensure a gap between floor and start of plasterboard or fit tight all round? Any advice welcome. Many thanks Bron

 

[Alastairreid]

No need to fit dpm with foil backed boards, keep your plasterboard 20mm clear of the floor when fitting.

 

[Notch7]

I was going to celotex with 50 mm then use foil backed plasterboard but do you think I also need a polyethylene DPM over the studs before the foil backed plasterboard or not

Without knowing the full construction detail it's hard to know exactly what you are trying to achieve.

In general foil backed plasterboard or polythene sheeting used on the inside is acting as a vapour control layer not damp proofing.

You could foil tape over all the celetex joins - including around studs to make a full VCL and then fit foil backed plasterboard too.

Foil backed plasterboard won't be impervious to vapour if you have electric sockets or rad tails.