To me near enough every abandoned building in Northern Ireland is just destroyed with graffiti etc, I haven't been to one that hasn't been and I've been to a few. Would like to get talking to people who have been to good ones.
Old schools have been disappearing fast, my two fav's where sold off and flattened for new development recently, I have been told this is a policy to 'monetize' all un-used assets by Ed Auth, so the chance of coming across others is a diminishing probability.
There's loads of places to visit, just have to get out there and find them. The more you do it the more you'll come across. Every city, town, village and also going to and from has something to explore.