Castellmynach is a grand late medieval mansion remodelled in the early seventeenth century, and altered later. On the north side of the house (NPRN 300587) is a large yard or court with an L-plan range on its far side. This consists of a grand seventeenth century north-south range, altered first as a farmbuilding and then as a residence, joined to a long east-west seventeenth century farmbuilding range. Both this and the house are now engulfed in a modern housing estate, but something of their original setting can be discerned on the 1st edition OS County series (Glamorgan. XLII.3 1880).
The north-south range was a two storey building with battered stone rubble walls and freestone quoins and other dressings. On the west side there is a large two centred arch flanked by mullioned windows with very narrow lights under dripmolds. To the south is a doorway with a two centred arch. This grand entrance, possibly a gatehouse with lodgings, can be compared to the gateway incorporated in the east range of the house. The building was later fitted out as a threshing barn. Above the arch is a datestone reading:
TMK/1620/rep-aire/1833.
The eastern part of the east-west range is a late sixteenth-early seventeenth century barn and stable or byre. The western section was added in the later seventeenth century and housed a byre.

Source: NMR Site File

John Wiles 19.02.08