Thanks, we have a high hedge between the houses and both are fully enclosed back gardens, the only way I can see what's going on to that side of my house is via her back garden, accessed via her back door. She is allowing me to call in and see the cracks tomorrow to take pictures of them. She hasn't had to get planning permission. How would / could I stop her joining on to my roof and building up against the side of my house? Does the fact that we are semi's make a difference, ie. strengthen her case? Either way it sounds like this is going to cost me several €100, and potentially a big headache. I also don't want my tenants to be bothered by a dispute either. She told me she has engaged an architect so I'll ask to view the plans tomorrow while I'm there. I've never really had any dealings with her do date but would like to stay on good terms.
Thanks for the input.