Chimney broken its back

[reevesie]

there are damp patches in both bedrooms where the chimney stacks are and is particularly noticeable after rain. Had flashings,lead gutter replaced as well as pointing but the walls are still damp. roofer suggests that the chimneys have 'broken its back' , where the slate that runs through the stack has broken down letting water run down the stack and hence the damp bedroom walls. is this a common term or is he feeding me a load of bs? is there a way of reparing this w'out rebuilding stacks

 

[jbonding]

is there any vents on the chimneys, if not it might be condensation.

 

[masona]

Yes agreed, you may need to cap the chimney pot (ventilation type) if the fire is not in use and make sure you're getting circulation air from the fireplace to top of the chimney.
See this