Ian Stirling wrote:

I have 12mm un-foil-backed plasterboard over a 2" gap, to a 50cm stone wall.
It's a mite chilly, and I'd like to insulate it a bit.

Ripping out the lot, and replacing with plasterboard/celtoex/... is
obviously one option, but is "slightly" disruptive, and involves
a hell of a lot of work, as well as not inconsiderable expense.

Other ways.

The quick and dirty way might be a few cans of expanding foam filler.
The trickey thing would be making sure you get even coverage though.

Not ideal from a decor point of view, but you could just stick foam
backed plasterboard on top of the existing plasterboard.

--
Cheers,

John.

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