This substantial structure likely dates from the late medieval period, when such fortified residences were essential for local landowners seeking protection in an often turbulent countryside. The building represents a typical evolution seen across Clare, where many tower houses were adapted for more comfortable living as the need for defence diminished.

The castle’s most striking feature is its integration of different architectural periods; the original tower house core remains visible despite extensive 18th and 19th century alterations that transformed it into a more conventional country residence. These modifications included the addition of larger windows, which replaced the narrow defensive loops typical of earlier construction, and the insertion of domestic features that would have been unthinkable in its martial youth. The structure retains elements of its defensive past, including thick walls and remnants of what may have been a bawn wall, suggesting it once formed part of a larger fortified complex.

Today, Castle House serves as a tangible link to Clare’s complex history of settlement and conflict. Its transformation from fortress to family home mirrors the broader changes in Irish society following the Tudor conquest and subsequent plantation periods. While many of Clare’s estimated 200 tower houses have fallen into ruin or been demolished entirely, Coolistoonan’s survival, albeit in altered form, offers valuable insights into how these buildings were continuously inhabited and adapted rather than abandoned, making it an important example of architectural continuity in rural Ireland.