According to a 1609 land grant to Sir Robert Nugent of Walshestown, this site once held Dysart Castle and its bawn, along with an impressive manor complex that included a hall, stone fortification, lough, stable, two barns, a haggard, forty dwellings, fifty gardens and a fish pond. Aerial photographs from 2011 reveal numerous earthworks in the fields surrounding where the house ruins appear on 19th century maps, particularly east of Dysart church and graveyard, hinting at the layers of settlement beneath.

The castle that Sir Robert Nugent acquired may itself have been built atop an even earlier fortification; an Anglo-Norman earth and timber castle that by 1302-03 was already described as ‘a small, weak, and ruined fort’. This fort belonged to Ralph Pippard, lord of Dysart manor, whose family had held these lands since the early 13th century when William Pipard received them from Walter de Lacy. The strategic importance of Dysart is evident from Hugh de Lacy’s decision in the late 12th century to retain personal control of the ‘lake and vill of Dysart’ whilst granting away the surrounding barony of Magheradernon to William le Petit. The lake mentioned in this medieval grant might be the same pond identified 240 metres west of where Dysart House would later stand.

Archaeological evidence suggests the Anglo-Norman fort took the form of a ringwork rather than a motte and bailey castle, as no motte-like earthwork has been identified near Dysart church. However, a group of three sub-triangular earthworks and remnants of a field system 420 metres south of the church and graveyard may represent traces of the original Anglo-Norman manor. When Ralph Pippard sold Dysart Manor to King Edward I in 1301, an inquisition the following year found the fort and its messuage to be worthless, yet the site would continue to attract noble residents for centuries to come, each generation building upon the foundations of the last.