my girlfriend had a damp patch in her flat that was being caused by a number of factors, 1 a cracked gutter, 2 a leeky window and 3 a build up of crap in the wall/under floor.
The only comunal part is the gutter. This will be listed in the title deeds of your property.
The fact his flat is suffering from damp is his problem, the damp course is a dubious one but when we asked a few damp specialist companies to quote they all said it would be my girlfriend’s responcibility and not communal expense, i asked this question to them all as the expected cost was high and the answer was the same every time.
If the roof leaked and you had to fix a ceiling do you think he would pay???