By Jazzbobrown
United Kingdom 
We have a clematis montana planted against the back of our neighbours garage, We are aware that they can be invasive & keep it at a maximum of 9' high - about an area of 2' x 1' flops over to the top of his garage roof which is of flat felted construction.
Our neighbour says that this is causing damp.No shoots are allowed to grow up & under the felt overlap.
Will the plant cause damp on top of his roof in such a small area under these circumstances?
Thank you - Michael.
8 May, 2011
Answers
Since this is his garage and on his property No part of you clematis should touch it and certainly not flop over the top.
10 May, 2011
If the garage felt roof is in good order, and no shoots have been allowed to go under the felting, then I see no reason why this clematis should cause damp. But then as it his garage roof, and he obviously has problems with dampness in his garage, you need to support the climber in some other way. Maybe a picture of the garage area would result in some advice to help you.
9 May, 2011