In 1865 the castle was described as following; ‘The Castle of Dunnaman consists of a massive oblong tower, surrounded by a wall now nearly destroyed. The tower is 46 ft. in length by 33 ft. in width, and is only 31 ft. in height to the present summit of the wall, which clearly was never much higher; but there may have been apartments in the roof, as can be seen in the much more lofty tower of Annadown. The peculiarities of the building, among which may be reckoned the immense thickness of the walls in proportion to the size of the tower, are well seen in the two accompanying ground-plans. The walls are 8 ft. in diameter, or about double the thickness of those which are generally to be found in Irish mediaeval castles.
The entrance door leads into a narrow passage, in the roof of which is a square hole from 2 to 3 ft. in diameter communicating with the room above. This is popularly called the murdering hole, and was evidently used for pouring or flinging down missiles on the heads of assailants. There are two round holes in the door; one in the moulding of the jamb, and another at the top of the arch, which would serve, cither for shooting through, or as a spy-hole. The jambs are ornamented with punched work, the pattern on one side being in squares like a chess-board. To the right of the passage is a small room, 8 ft. long by 5 ft. 6 in. wide, which was probably used as a guard-room: on the left is a spiral staircase.
The principal chamber on the ground-floor is 32 ft. long, by 17 ft. wide; lighted merely by three loopholes very widely splayed, and contains no fireplace. It is covered by a vault, which, up to about one third of its height from the springing, is constructed of wrought stones laid horizontally, corbelling out one over the other, and of which the soffits are cut to the form of the arch. The vault above these wrought stones is composed of rubble thrown in from above on to the centre, which was afterwards removed. There are corbels in the walls for supporting the beams of a floor, and additional loop-holes above this level, so that there were two stories beneath the vault.
Over the entrance passage and guard-room, and on a level with the floor just described, is a small room 14 ft. by 8 ft. 6 in. entered from the staircase in a peculiar way, which cannot well be shewn on either of the ground plans. Above the door opening to this room, the staircase leads to the principal apartment of the Castle. It is of the same size as the vaulted room underneath, and contains a large fireplace and the only one in the building, and is lighted by three narrow windows. From this room a passage communicates, in the thickness of the wall, with a garderobe. Near the fireplace, a short and narrow passage leads to a small room of the same dimensions as, and immediately over the one already described. This room is lighted by a window 1 ft. in width, the largest in the Castle, the splay or inner arch of which is formed of finely cut stone, similar to the splay arches in the Prior's house of the Franciscan Priory, Adare. No traces of the construction of the roof remain; but there is a square hole on the summit of the western wall, in the centre of its breadth, which communicates with the garderobe shaft below, and was apparently constructed for the purpose of flushing it from above.
Among the windows are examples of round, square, and ogee heads; the dripstones over those in the two small rooms are very singular, and characteristic of Irish buildings of the fifteenth and sixteenth centuries.
