What do you do when your neighbour doesn't want to contribute to a new roof when his side doesn't have the leak?

 

My tandem garage is adjacent to my neighbour's and the two garages share the same 20ish year old felt flat roof. The drainage channel is just off the centre line between the garages and on my side. The single drainage down pipe is in my garage. The drainage channel is leaking into my garage at the lowest point where the down pipe is.

I've already had it repaired but the repair has failed and the roofing company isn't interested in honouring their 5 year guarantee after 4 years. 

 

I think it's common knowledge that joins between a new flat roof and an adjacent old one is a bad idea but short of paying for it all myself I can't think of a solution. Has anyone come across this situation and found a solution? If I could, I'd love to separate the two roofs and have a GRP roof on my side with a brick parapet separating the two sides. The parapet could just be an upward extension of the single brick wall that separates the two garages. This however would mean disrupting my neighbour's side.

 

Thanks in advance

 

27 minutes ago, Steve1309 said:

My tandem garage is adjacent to my neighbour's and the two garages share the same 20ish year old felt flat roof.

Check your deeds - there may be provision for repairs

 

22 minutes ago, Steve1309 said:

I'd love to separate the two roofs and have a GRP roof on my side with a brick parapet separating the two sides. The parapet could just be an upward extension of the single brick wall that separates the two garages. This however would mean disrupting my neighbour's side.

I'd imagine that should be possible under the Party Wall Act, if you can get planning permission.