The National Inventory of Architectural Heritage's website is a great place to start. The NIAH identifies, records, and evaluates Ireland’s post-1700 architectural heritage, providing the basis for Records of Protected Structures. On their website, you can search buildings, gardens and surveys by county or you can use their mapping tool to find records of both the National Monuments Service (Sites and Monuments Record) as well as the National Inventory of Architectural Heritage.

You can also find An Taisce's Buildings At Risk register here.