The monument consists of the remains of Gilbertfield, also called Gilbertfiled castle, a seventeenth century L-shaped mansion situated on the lower slopes of Dechmont Hill.
The remaining structure is rectangular, the SE wing having been demolished. The four-storey house is aligned N-S and measures 14.6m by 8.5m over walls 0.9m thick. The walls are complete to wallhead (10m) although they are showing signs of decay. There are two crowstepped gables intact to a height of 17m, one in the N wall and one in the S end of the W wall. In the NW angle there is a corbelled turret. The masonry is coursed sandstone bonded with lime mortar. The entrance is in the E angle. The lobby is partly rubble filled as a result of the collapse of the stairs. This passage leads to the main newel stairwell. The rooms in the ground floor were all vaulted but only that over the N cellar is intact. The kitchen was in the demolished SE wing. The dining room took up the S portion of the
first floor and was connected to the kitchen by a service stair in the SW wall. The N parlour is accessible through a corridor that runs parallel to the main staircase. There were three bedrooms in each of the two upper floors. Large windows light the S, W and E sides, two of which have decorative gun-holes in their sills. The main staircase has several smaller windows.
The area to be scheduled is square with sides measuring a maximum of 30m to include the mansion, as shown in red on the accompanying map.