The feature is an eight-metre square platform, oriented along its northeast-southwest and northwest-southeast axes, sitting at the northern angle of a moated site. That combination, a domestic structure tucked inside a moated enclosure, is quietly telling about how people once organised both shelter and security in the Irish midlands.

Moated sites are a particular feature of medieval Ireland, most common from the thirteenth and fourteenth centuries. They typically consist of a raised platform or enclosure surrounded by a water-filled or rock-cut ditch, and are generally associated with Anglo-Norman settlement, often the homesteads of lesser landowners or free tenants rather than great lords. The platform at Carnan sits within just such an enclosure, at its northern angle, and the slight elevation of the ground there is interpreted as the footprint of a house. The site was noted as a rectangular house site as far back as 1976, which gives the identification a degree of continuity even if the date of the structure itself remains unresolved.