Original house at Lower Cosmeston Farm

Lower Cosmeston Farm is a two-storey farm building range that was originally a house, aligned roughly east to west. A gabled single-storey wing has been added at right angles to the south front elevation. The building is constructed of rubble limestone with brick and block dressings, and it has undergone various repairs and additions. It is topped with a corrugated tin roof.

The southeast corner has been rebuilt in block around a 17th-century gable stair. An extension with a mono-pitch roof has been added to the right, featuring a wide door at the angle with the main range. A further, much later extension has been added on the east side. The right gable includes steps and a door leading to the upper floor, while there is a lower door to the east end. The east gable has a large projecting stack, which has been rebuilt at the southeast corner and is capped with brick. The north elevation is largely obscured by vegetation but features a corrugated tin lean-to at the west end, with blocked window openings visible from the 17th-century part.

The south elevation has three doors on the ground floor: a wide cart door to the right, a narrow central door, and a wider door to the left, which is flanked by a window and has a window above. There is a small square window above the central door, and a single-storey extension is located to the right.

Entry to the earliest part of the building is through the right-hand cart door on the south elevation. Inside, there is a large fireplace and a stepped stack in the east wall, along with a boarded-over doorway opening to the northeast corner, which is an early entrance. A beam is built into the east wall, recessed above with joist sockets, a lintel, and a small blocked opening in the wall above. There is also a doorway opening and evidence of a central window opening in the north wall, which is heavily damaged.

The later 17th-century extension retains a gable fireplace that is now infilled, featuring a massive timber lintel and stone jambs. The gable staircase survives to the left, but the upper floor is inaccessible. There is a blocked doorway leading to the earlier house. The east gable has a projecting stack and a corbel table at ceiling height. The east extension includes a door from the early part and a secure room built into the southwest corner. Although the floor has been replaced, the end beams with joist sockets remain, suggesting a narrow framing floor structure.

The southern extension features a gable fireplace and a small cast iron grate.