damp and old render

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Hi, I have bad damp/black mold in my bedrooms. I ventilate the room every day and use a dehumidifier in for 2 hours in the morning and evening. I have air vents in my roof, vented sofits, new fascias and good eaves with EPS installed. The render on the house was done by the previous owners back in 1985. The gable end has a (Y) shaped surface crack. Do you think the mold & damp is due to condensation not breathing through the render? I would like to remove all the render and replace with a new render. One plasterer said that this doesn't need doing, and another said it did! Is it possible that the render is retaining moisture which is causing the severe damp? Any advice will be welcomed, also advice on best the types of render will be welcomed. Thank you
the black mold is condensation. the spores of the black mold are a health hazard.
clean the mold of with dettol mold spray from most supermarkets. move the furniture away from the walls so that air can flow, open a window and turn the heat up in the room.
If you've got cracks in the render its gonna let water get behind the render and with no where to go it will start bleeding through the inner leaf, also when the temperature drops to freezing that moisture will expand opening up the render even more. The mould will be condensation probably from the cold spots on the gable wall.
I would create a warm wall in the rooms if you can afford to lose 3 inches,fit a mechanical stud to the wall leaving an air gap,infill with solid insulation ,plasterboard and skim. Also fix the crack, I have a PIV fitted in my house ,it helps a lot ibelieve
The damp ingress will cause the cold spots and as such contribute to the condensation problem.

All the above is sound advise.
Is the wall north facing ? all external walls are colder than internal.

What you need to do is see how much insulation you have in the loft also, I always recommend to bring the insulation value up in a house as it helps with condensation.

Keep kitchen doors and bathroom doors closed when in use and also at least 30 mins after use.
Fit a humidistat fan also.

Condensation is easy to cure, its just usually more than one thing that causes it, like carlos said damp patches are colder hence they can become dew points.
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