The building at Ballythomas in County Laois was described in the nineteenth century as a seventeenth-century house that had been remodelled, and in that remodelling one of its upper floors, along with its castellations, was removed. Castellations, the battlemented parapets associated with tower houses and fortified dwellings, were common enough on structures of this period in Ireland, part defensive feature and part status symbol. Their removal here speaks to the way houses of this age were quietly domesticated over time, stripped of the architectural vocabulary of an earlier, more anxious era.

The house was the home of Lord Dunboyne, the Bishop of Cork, a connection that places it within the complicated world of post-Reformation Irish ecclesiastical and aristocratic life. What survives today is a two-storey rendered structure, roughly six metres wide and just over fifteen metres long, its exterior finished in pebble-dash. The front elevation carries a dressed cut-stone doorway with a keystone, four rectangular windows at ground level and three above. A curtain wall, the kind of enclosing boundary associated with defended or semi-defended properties, extends westward from the house and terminates in a single pillar, the only remaining trace of what was once a more complete enclosure. None of the original outbuildings have survived. Around the northern gable, some old cobbling is still visible at ground level, a fragment of the yard or approach that once surrounded the property.

The building is an occupied dwelling rather than a ruin, which accounts for both its survival and the changes it has absorbed. That combination of continued use and gradual alteration is itself a kind of history: a house that was never abandoned, never left to fall, but that arrived in the present considerably altered from what it once was.