Damp coming from Chimney Breast

if the fireplace is blocked off you will need a air vent to maintain air flow through the chamber

The fleshing around the stack above the roof tiles. My be letting rain water run down the stack and past the fleshing. Or there is a hole in a roof tile that's letting water in...

Have you checked to see if there are lead trays (not lead flashings)? Lead trays are designed to stop damp from the chimney stack entering the roof void. Many older properties did not have these which was not such a problem when the fireplaces were used regularly as the heat from the fires kept the damp at bay.

If you are still getting damp or condensation - if it is capped, air vents will help reduce the problem but not get rid of it. It is a temporary solution, however it also depends on the build type of home and type of mortars used. Ideally an inspection should be made to outside wall of chimney breast to see if and mortar worn away or cracks which allow water to ingress. Sometimes this can also be due to a blocked upper roof gutter and water entering through roof. Also in a case we experienced, chimney capped, cement fillets around base of chimney stack and onto tiles was letting in water through side wall of chimney stack and into house. We tooth in lead around the base of the stack and onto tiles.. This cured the problem and this client did not have vents in chimney. However, adding them there is no harm.

Hi, As Robert has just described. If your chimney is capped off, this will create a cold void inside the chimney. This will cause condensation in the house to go straight to it. Especially as your chimney is on the gable end and is exposed to the elements as you say. As Robert has suggested, you need to vent the bottom and top of the chimney to create airflow. But with the chimney being exposed I would also advise covering the chimney inside (upstairs) with an insulation paper. Maybe a couple of coats of polystyrene on the roll and then cover with lining paper and paint to suit. Or standard wallpaper to match. So, you are venting the void and giving the chimney a warmer surface inside, so as to not attract condensation. If you suffer with condensation throughout the winter months, you might want to try leaving a couple of windows slightly open whilst you have your central heating on. This will allow the condensation to escape out of the window. Condensation will always find the coldest spot in your home. So let the cold spot be outside via the open window. Extractor fans in bathrooms and over the kitchen hob are also a must. Good luck! Regards Paul