wet behind insulated plasterboard

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I live in a 1902 terraced with 9" solid wall that was previously damp. After consulting this forum, i was advised to tanking slurry followed by dot and dab insulated board.

I've put 4 layers of tanking slurry on and thoroughly dried for 2-3 weeks.

The plasterer has installed insulated plasterboard via dot and dab, and left a 2 inch gap at the bottom so it can dry/ventilate

If i put my hand up the back of the insulated plasterboard, there is water on the back/bottom of the insulated board

It has not come through the insulation and plasterboard. Before the PB was installed, the wall never felt wet to touch, just cold feel after it had rained.

Any idea?
 
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Are you sure it is not condensation? The wall behind the insulated plasterboard will now be a cold spot and the gap will allow the air to condense on it.
 
possibly yes - and because i don't have a radiator in the room yet is this why?
 
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There is probably a fair bit of moisture still leaving the tanking slurry. There will always be moisture in the house and at this time of year always a cold spot it will condense on, unless you can rid of it via ventilation. Heating an area will just make it not that area that condensing happens. I am far from an expert, but I would say that if you are having work done like tanking/plastering there will be an excess of moisture around that will be more of an issue at this time of year due to low temperatures which may not be an issue going forwards.
 
Not an expert, but it occurs to me that in the short term it might be useful to have the gap for the tanking to fully dry, but in the long term an air gap from a warmer room to a colder are behind insulation will lead to condensation. I'd personally be inclined to seal the gap in late summer when it's likely to be drier. But as I say, not an expert.
 

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