I'm having a bit of a mare currently. Over the past year I've been getting some really bad damp patches and blown plaster on chimney stacks in two upstairs rooms where the chimney stacks combine to one external one on the roof. As it's a 120 year old house the moisture is also bringing all the salts from the historic burned fossil fuels through the wall too making a bit of a mess.
I've spoke to a damp proofer, he say's it's water getting in through my external stack, having spoken to a roofer, he says the stack looks fine (though he didn't get up to have a proper look...). I'd be inclined to think it's definitely a leak somewhere on the stack and get a better roofer out. Just wondered if anyone had any tips / advice. I'm half debating just getting the stack removed as it's not in use. You can see there are external vents to the outer wall at first floor level and they are also at ground floor level.
The pics give a good idea of what is going on. It's a big old stack.