The monument comprises Craignethan Castle of medieval date, visible as an upstanding building. The monument is in the care of Scottish Ministers and was first scheduled in 1920. It is being rescheduled as no adequate documentation survives from the time of the original scheduling.
Craignethan Castle was an important artillery fortification with an exceptional residential tower. Its construction by Sir James Hamilton of Finnart, an illegitimate son of the 1st Earl of Arran, began about 1530. The castle may be founded on the site of an earlier 13th century castle. It was acquired by the 2nd Earl of Arran in 1542, who was banished to France in 1566. His castles at Craignethan and Cadzow were then occupied on behalf of Mary Queen of Scots until her enforced abdication in 1568, when Craignethan was surrendered to Regent Moray. There is no reference to Craignethan being besieged then, or later that year when it was retaken by the Hamiltons. It was again prepared for siege in 1579. Its present state is a result of the comprehensive demilitarisation that followed in the years around 1580. Orders were given to slight the main defences, including the demolition of the great western rampart above the inner ditch. The main life of the castle was thus short-lived, only 50 years. The castle remained in use in some form until 1659 when it was bought by Andrew Hay. He built a new residence and domestic range within the outer court, which contains a dated inscription of 1665. The castle was later associated with Tillietudlem Castle of 'Old Mortality' fame, as created by Sir Walter Scott.
The castle is situated in a striking and inaccessible position, on a spur formed by the deeply eroding beds of the Water of Nethan and the Craignethan Burn, between c.65-125m OD. On three sides the ground falls away steeply to ravines, but on the W, at the base of the spur, the land rises sharply to overlook the site. The castle comprises a central towerhouse, within an inner courtyard defined by a rectangular barmkin wall with towers on all four corners, a tower in the middle of the southern wall and a gate tower positioned in the centre of the northern wall. A later outer courtyard is present to the W, separated from the towerhouse by a large rampart and a N-S ditch containing a 'caponier' and traverse wall.
The towerhouse was constructed in the 1530s and measures c.16m N-S by 21.2m E-W, with walls c.2.5m thick. It stands to a height of c.10.6m (to the bottom of the parapet). The parapet rises from a double row of corbels, arranged in chequer pattern, with turrets at each angle and in the middle of the W front. The openings on the western (exposed) side of the building are small in comparison to those on the other three sides. An entrance door in the western wall leads into a transverse passage, from which opens a stair at each end (one leading down to the basement and another up to the higher floors and parapet), a hall, and a serving hatch to the kitchen. The hall is barrel-vaulted and measures 9.37m E-W by 6.25m N-S by 7.4m high. It has a narrow gallery on its W side, originally entered from a stair in the SW angle of the building. The fireplace only survives as a fragment in the NE of the hall, where it adjoins the door to two superimposed chambers, both with garderobes. The kitchen, containing the remains of a great fireplace in the eastern wall, is now only entered via a separate stair from the basement. The upper floors of the towerhouse are accessed via a stair in the NW angle of the building, which opens into a timber-floored room above the kitchen. Above is an attic storey with four rooms. The basement is accessed via a stair on the SW angle of the towerhouse. It comprises four storage vaults, with a fifth, smaller vault towards the SE, which contains a well and may also have been used as a prison.
The barmkin, or inner courtyard wall, encloses an area of c.50m E-W by 25m N-S. It has moderately thick walls (c.1.8-3.2m) around its less vulnerable N, E and S sides, and is flanked by rectangular towers. Two entrance gates were present through the courtyard wall: one through the S front, which was blocked up and succeeded by the entrance in the gate tower in the middle of the N wall. Here, there are well preserved stone setts around the tower, and beyond it to the W, leading to the site of the bridge. The setts were bound by a slight wall, probably an addition made during the ownership of the Duke of Chatelherault. Two double-gated traverse walls were also present, running N-S between the towerhouse and the N and S courtyard walls, set back slightly from the west front of the towerhouse. These were demolished c.1579.
The NE Tower is now ruinous, but recent excavation suggests that there were two distinct phases of use within the basement of this tower. It was initially used as a kitchen (the large fireplace on the E wall of the room was typical of those in the kitchens of important households), and later to house some other domestic, or perhaps industrial function. There were two entrances into the NE Tower at first floor level: one from the W and another at the E end of the S wall, where a spiral stair had led to the floor(s) above. A short passageway led to a single chamber of private accommodation.
The SE Tower is the best preserved, with a basement, a high vaulted chamber and a roof with access to the high-level loops. Though called the 'kitchen tower', it is possible that the chamber was originally designed by Sir James Hamilton as his chapel. The E range basement is reached via stairs near the NE angle, leading down to the vaulted-over alley which terminates at the postern through the S curtain. The basement vaults were open from the passage, and used for storage and as a workshop or smithy. Recent investigations suggest that the E range was never built above basement level and no trace of the putative S range, other than blocked windows in the curtain wall, have been uncovered, although such evidence may have been removed by later developments. It is possible, therefore, that the original layout of the castle did not include provision for the towerhouse and that the S and E ranges had been earmarked as its principal accommodation. The implied change of building strategy could have centred on the decision to build the towerhouse.
The inner courtyard and towerhouse were shielded by the W rampart and ditch, which run N-S and across the neck of the spur. The W rampart comprised a massive stone wall measuring c.5m thick. It appears to have been well armed, with loops above its now-surviving height to command the site of the outer courtyard, and embrasures at its parapet. The guns which the rampart was designed to accommodate seem to have been heavier than the hand-held weapons of the loops elsewhere, and may have included 'double-falcons' of about 65mm calibre mounted on carriages. The ditch measures c.9.5m wide and is bounded by a vertical counterscarp wall. Towards the southern end of the ditch are the remains of the caponier, which runs E-W across the base of the ditch. Externally this has a low profile with a stone roof; a few of the original roofing slabs survive at each end. It has three loops for handguns on each side. On the northern side, the outer loops are oddly angled upwards. The loops open internally to a vaulted gallery, entered from a turnpike stair within the rampart. The roof of the caponier is protected by a loop just above its ridge, opening internally to the access stair.
Towards the northern end of the ditch are the remains of the traverse, an addition to the works made between 1542-79. It comprises a loopholed traverse wall extending right across the ditch. Originally it had a heavy timber roof (the corbels which supported the plate or timber beam to which the roof was fixed survive), and it was open to the rear. The interior, unlike the caponier, was well-ventilated. The traverse was reached via a stair inside the contemporary square turret attached to the W rampart.
The outer courtyard lies to the W of the towerhouse, inner courtyard and western defences. It was an afterthought to Sir James Hamiltons' original works of c.1530-40, and was almost certainly made during the ownership of the 2nd Earl of Arran and Duke of Chatelherault, Sir James' half-brother. The outer courtyard encloses an area of c.55m N-S by 46m E-W. It was protected by low crenellated walls to the N, W and S, with square towers at the NW and SW angles. It was entered by a gateway in the centre of the western front. A secondary door flanked by loops was cut through a W face of the NW tower before 1579. The walls and towers contain large numbers of gunloops, systematically placed so that the whole circuit could be protected by fire.
The house and its associated ranges in the NW of the outer courtyard were built by Andrew Hay, the Covenanter, in 1659. It has two stories and an attic, with a projecting round stair and entrance dated 1665 on the door lintel. To the rear it takes in the 16th century SW courtyard tower, which has been consequently raised in height. An E wing is reduced to a shell. A single-storey range, including a kitchen, now ruined, adjoins the house against the W curtain. The crow-stepped gables are made from corbels taken from the 16th century towerhouse. Perched on the N gable of the intact part of the range is a weathered heraldic beast, which may have been designed to stand on the towerhouse roof. Inset in the gable is an almost illegible stone bearing the Hay arms.
The area proposed for scheduling comprises the remains described and an area around them within which related material may be expected to survive. It is irregular in plan, bounded by the River Nethan to the E, with maximum dimensions of 324m from the easternmost to the westernmost points, by 246m from the northernmost to the southernmost points, as marked in red on the accompanying map. The area proposed for scheduling is exactly the same as the area of the Property in Care.