Pointing below damp proof course, and damp patch on wall.

[speedfox]

Hi, I have two issues with an external wall. One issues is that the pointing in the brickwork below the damp proof course seems to be in a bad state of repair. The other is that there is a damp patch on the wall behind the chimney breasts, and it seems to have an odd "rainbow" shape to it. The wall itself has a thin layer of cement repointing over top of the original lime mortar

My questions are
* What could possibly be causing the damp patch, and is there any connection to the pointing issue?
* sub question: The owners of the downstairs flat (I live upstairs) have mentioned something about "removing rubble" from the chimney breasts when they did their renovations. Did that rubble need to be there and if so, now it's gone, what should it be replaced with?
* Does the thin cement repointing need to come off to fix the patch on the wall?
* Can the pointing at the base of the wall be fixed by simply cleaning out the old mortar and putting fresh lime pointing in with a pointing gun, or is there a special process needed for the base of the wall?

Thanks in advance for the help.

 

[opps]

Do the presumably boarded up fire places have internal air vents? Does the chimney pot have a vented cover?

This is not my area of expertise, but I am guessing that those in the know may well ask those questions.

 

[speedfox]

There seems to be some sort of air vent on the external walls for one chimney but not the other. I haven't seen any air vents for the chimneys inside the building.