It seems that when our cavity wall cowboys installed the insulation recently they 'accidentally' drilled into one of our chimneys. They spotted this and filled in the holes in the bricks/mortar from the outside. However a gas installer fitted a fire last week and spotted there was further damage on the inside of the bricks where the drill had taken a bigger chunk out of the inner side of the brick. The gas bloke filled in the other side of the brick he could see within the fire place but said the others further up teh chimney could be damaged the same.
he suggested that the chimney wouldn't function correctly and that fumes could seep up the bricks somehow and then filter into the loft. (I'm paraphrasing what my wife has told me the installer said).
What I can't understand is how or why the damaged bricks would affect the chimney, even if the bricks have vents in them the fumes can only reach the next layer of mortar surely? Do I need to take out all teh damaged bricks and replace or is he thinking something else is wrong.
I'm considering dropping a carbon monoxide detector into the loft to see whether anything is seeping for the time being but just don't fancy damaging the chimney any more than the cowboys did iin the first place.