Castellmynach is a grand late medieval mansion, remodelled in the early seventeenth century and largely refenestrated in the late eighteenth-early nineteenth century. A sixteenth-seventeenth century and later complex lies to the north (NPRN 37489). The house is now engulfed in a modern housing estate, but its former layout is recorded on the 1st edition OS County series (Glamorgan. XLII.3 1880).
The house is an L-plan building made up of a south and east range. These enclose two sides of a small walled garden which may have originated as a seventeenth century court. The south range housed a ground floor hall, open to the roof, but with a floor inserted in the seventeenth century. The arch-braced hall roof survives. Either side of the hall are two storey blocks with great end chimney stacks. The western block housed the cross passage or services. The east range has blocked opposing four-centered arches towards its southern end. This gatepassage was the main entrance to the medieval house from the east, where it aligns with a drive depicted in 1880. On the east side the ground floor has small windows, one with a trefoil head and hoodmold. There are two mullioned windows, one now blocked, on the upper floor.
The interior retains many seventeenth century and later features, including an interesting array of wallpaintings.

Sources: RCAHMW Glamorgan Inventory IV.1 The Greater Houses (1981), 353
NMR Site File
CADW Listed Buildings Database (13517)

John Wiles 19.02.08