I'm sorry this may sound long-winded...
One of my leaseholders had alterations done some time ago to the flue of their gas boiler which is installed vertically from the ground floor up through the chimney of the building - which is a terrace converted into maisonettes.
They replaced what had been a compliant and effective metal cover that allowed for the safe release of their emissions at the top of the chimney, and also kept the chimney watertight and sealed from wildlife.Their plumber however removed this and installed an air intake pipe that made it impossible to protect the chimney from rain and the chimney pot has been left open for some time. The installation seems to have required the removal of the chimney pot from the chimney block leaving the cement crown damaged and the pot repositioned with poor workmanship evident.
I have asked the leaseholder on several ocassions to fix this so that the chimney could be protected from water ingress. No permission was sought for the work or for access to this part of the building which is not part of their premises.
Their flat is currently unoccupied as they sublet and their gas safety cert expired on 31 Dec due to non-compliance with the new flues in voids regulations - as such their boiler has been labelled "At Risk" by GasSafe and they are investigating ways to reflue to comply.
Do I have the right to call my own plumber to disconnect their flue extension and protect my building from water getting in every time it rains? There is already much tension with this leaseholder as they seem indifferent to their obligation to obtain permission for any work that affects the building. I want to make sure that I don't overstep what I may legally do. They have been asked to do something about this for several months.
Thank you for any advice.