Overboard plasterboard with thermal plasterboardboard Information, help, tips and advice on cavity walls, ceilings and lofts etc....

[SusieRose]

I live in a "Cornish house" The House used to be PC concrete on the ground level . This was changed to Cavity( brick & thermalite) in the '80s. The 2nd floor is tiled with an air cap that runs all around the house.(mansard roof) I have learned the top is insulated with polystyrene & plasterboard on one side, but the other side is just Plasterboard!!!. Can I overboard with thermal plasterboard or do I have to rip all of the plasterboards off ( I hope not) to achieve some type of thermal insulation for the house?

[stoneyboy]

Hi susierose,
The issue is whether condensation will form in the original plasterboard if you leave it in place. You could minimise this by fitting a damp proof membrane (DPM). The construction would then be: old plasterboard; expanded polystyrene; DPM; new plasterboard.
Regards S

[SusieRose]

Thank you for the reply, it has helped me a lot. I did wonder about the condensation due to the cold air travelling inside and up to the loft area.

[stoneyboy]

Hi susierose,
You need the air movement in the gap all round you house to remove condensation.
Regards S

[SusieRose]

Why is PIR board not useful instance, it has the foil protection to help with condensation.

[stoneyboy]

Hi susierose,
Foil faced PIR board will work but it will cost you £10 extra per 1.2m x 2.4m sheet.
Regards S

[SusieRose]

Thank you for your expertise. I will follow your first reply to try and get some form of thermal insulation using the products you have stated. Thank you very much.