Freezing bathroom, black mould, help!

[Alwaysaware]

As above really we have an awful problem with cold external walls in our bathroom, black mould grows wherever it can despite me having trickle vents open and radiators on, vacumming the condensation off windows etc.

We are due to refurbish the room and we feel it needs to be stripped back to the blockwork as the plaster has gone all chalky and wont keep a coat of paint on it.

Would it be possible to dot and dab an insulated plasterboard over the walls to minimize the cold bridging? Will this work or will it create dame behind the plasterboards over time?

Any advice would be greatly appreciated. Id be happy to install a mechanical vent fan but not sure whether electrics running through a bathroom is a problem?

Thanks in advance

We have a fan that comes on with the light and stays on for several minutes after the light is switched off. We also have all the problems you describe.

I shall watch this thread and see if anyone has any good ideas.

Have you checked the walls outside the bathroom, ie is there a leak/blockage in your gutters causing water to penetrate the wall from the outside or damaged brickwork?
I wouldn't put insulated plasterboard on now until you have found and treated the cause of the mould because it will simply keep growing behind the new plasterboard and you will basically be throwing good money down the drain.
I would strip it back to the bare bones (when you refurbish) and treat any mould you see with the appropriate products and allow time for it to dry out and then add your layers of plasterboard.
Install extractor fans - we have two in our main bathroom - one above the shower and one at the other end of the bathroom near the sink and bath. A bit like this:
www.tapwarehouse.com/product/32200?

You can also buy mould-resistant products to help prevent it getting so bad again.

www.diy.com/departments/unibond-anti-mould-white-kitchen-bathroom-sealant-300-ml/1474132_BQ.prd
www.diy.com/departments/ronseal-problem-wall-paints-white-silk-anti-mould-paint-750-ml/127222_BQ.prd
The Dulux bathroom range of paint also has anti-mould properties.
www.dulux.co.uk/en/products/dulux-easycare-bathroom-soft-sheen

Our bathroom has one outside wall and another that has a double glazed window the width of the wall with the bath below. The outside wall also has the airing cupboard which contains our hot water tank.
We live in an all electric house and the bathroom is heated with a small night storage heater, and if required a wall mounted fan heater which we use very rarely.
When we refurbished the bathroom we decided to have all the walls fully tiled and 10 years on I can say that we have no mould issues at all. Granted we have no idea what if anything is going on under the tiles but the grouting is showing no signs of going mouldy and the sealant round the bath (which has an overhead shower which is used daily) is as white as the day it was done. We’ve just accepted that part and parcel of having a shower is that we give the tiles a quick wipe down afterwards
We have an extremely efficient extractor fan on the outside wall above the window and I also make sure that the bathroom window is left open for at least an hour or so everyday.
I know tiles aren’t everyone cup of tea but our mould issues disappeared when we had the bathroom refitted