I have had a condensation/mould problem that literally arrived one day about 3 years ago. I have a concrete ceiling above which is a walkway where the paving stones have cracked and there are a lot of pot plants I think the asphalt my have cracked but there is a dispute as to wether this is so and if so if it is responsibility of the council or the leaseholder above.Its an ex council property. There is a black line of mould that runs across the ceiling exactly on line with the walkway above and they tell me this is because it is where the heat difference is greatest. However I recently had the bathroom (the next room along) completely redone I gave the builder a bottle of mould killer/prevention stuff but he didnt use it said it wasnt needed although I feel he probably forgot to use it until too late. Anyway one month later mould is reappearing on the bathroom ceiling. The council told me that if the ceiling is concrete and if water is coming through from above it will definitely find its way through and drip as opposed to just coming through as damp and I cant find a drip anywhere. I am in the middle of redecorating again and am worried it will all be in vain. Is there an easy way to discover if the asphalt above has cracked and is it true about the water dripping. I have read all the condensation advice and keep airing but to no avail. If I have to treat the place for damp/condensation what should I use and how can I stop the mould. Any advice would be great.