It is listed as a monument, which in the Irish context places it in the company of sites considered to have archaeological or historical significance, yet the available documentation is thin enough that the full story of the house remains elusive.

The name Grannagh itself has deep roots in the Irish landscape, and houses bearing such townland names in Connacht frequently trace their origins to the post-medieval period, when landed estates reshaped the countryside and earlier structures were absorbed, demolished, or built over. Without more detailed records in the public domain, the specific history of this house, its builders, its occupants, and the phases of its construction or decline, cannot be set out with any confidence. What can be said is that its designation as a monument suggests something survives or once survived here that warranted formal recognition, whether that is a substantial ruin, a buried foundation, or the remnant of an earlier structure folded into a later building.