Neighbours garage connected to my wall

[carriesue]

Help needed please. My neighbours are renting property, their garage is connected to my outside wall and is causing damp. The gap between garage and my wall is 4cm, the asphalt roof is attached to my wall.
I have contacted the owners who sent their builder to have a look. He has stated to me that it is nothing to do with the garage (even though it is very old, but has caused no problems until the beginnning of this year) and that it is my problem. When entering the garage there is a crack in the wall, the owners have allowed me access to repair this! They have also stated that the garage will stay and that they have a right to do what they want in their garden. The problem is becoming worse and I do not know what to do next.
Many thanks

 

[mattylad]

Have you had your own builder have a look & identify the problem?

How can you be sure that it is the neighbours garage that is causing it?

What caused the crack?

 

[^woody^]

You need this looked at by an independant person, and the actual cause (and therefore responsibility) determined.

Get a local surveyor to report on the probelm, remedial action and responsibility.

Or get your insurers involved, and let them do the chasing