The site measures roughly 51 metres from north to south and 42 metres from east to west, marked out by an inner bank that rises about 30 centimetres above the surrounding ground. Between this bank and a possible outer bank to the northwest lies a fosse, or defensive ditch, approximately 2.6 metres wide and 80 centimetres deep. A causeway at the northern entrance would have provided the main access point across the water-filled ditch.

These moated sites, common across medieval Ireland, typically date from the 13th and 14th centuries when Anglo-Norman settlers established fortified farmsteads throughout the countryside. The rectangular enclosure would have contained timber buildings, perhaps a hall house and outbuildings, all protected by the water-filled moat. Such sites represent an important phase of Irish history when new agricultural practices and settlement patterns were introduced, fundamentally changing the landscape.

The monument has been under a preservation order since 1977, recognising its archaeological significance. The details recorded here come from the Archaeological Inventory of County Laois, published in 1995 by the Dublin Stationery Office and compiled by P. David Sweetman, Olive Alcock and Bernie Moran, with updates from more recent research. As one of many moated sites scattered across the Irish midlands, Garryduff offers a tangible connection to the medieval settlers who once farmed this land.