What is the cause of damp and white mould on my loft/attic roof.?
Could be a leak in your roof or inadequate ventilation. The heat from your house escapes meets the cold surface of your roof and condenses air needs to get into your soffits between your insulation and roof deck and escape at the peak. in your case(loft)depending on your ceiling you probably need continuous ridge venting that’s if your ceiling comes to a point no flat space over head if not fixed vents or turbine ventilators can be used its important not only that you have roof vents but soffit vents and unrestricted air movement. hope i explained this well enough. its a common problem with cathedral ceilings not done properly say you have 2×6 rafters your ceiling directly on one side your roof deck on the other if you have 6 inches of insulation you have no ventilation there you would need moore vents between the insulation and the roof deck to allow air to move these are contoured pieces of plastic or styrofoam plastic being easier to work with.
