Treflach Hall occupies a lofty site with sweeping views, beside a Lebanon cedar of considerable size. The house was the property of a branch of the Trevor family who descended from Thomas, the second son of Edward Trevor, Constable of Whittington Castle (d. 1537) and his wife Ann Kyffin. Although the house now bears a date of 1704 over the central upper window of the south front, this probably commemorates a remodelling of the existing building, perhaps by Richard Trevor (d. 1717) and his wife, Lowry Edwards (d. 1712). The house seems to date from the seventeenth century, although it is difficult to be certain. As it stands, Treflach is a U-plan two-storeyed house, with a south front of two-bay half-hipped, gabled wings which project slightly to embrace a tight three-bay recessed centre. It is built of limestone rubble stone bound by rusticated quoins. Lofty brick chimney shafts, with arcaded-panelled decoration, rise to each side of the entrance front, their stacks projecting from the body of the house and bound by the stone bands which run around the whole building.

On the north front there is a projection which was originally a stair turret, although the staircase has since been removed. The remaining staircase, rising at the centre of the house’s west side, blocks what would have been the kitchen fireplace. Of dog-leg form, it appears to have formed a part of the early eighteenth-century remodelling and has stout twisted balusters and heavy newels of a form more commensurate with the Jacobean era. A number of rooms still retain early eighteenth-century panelling, whilst an ambitious painting of the marriage of Neptune was recorded as being upon the ceiling of one of the sitting rooms in 1907, when it was described as having: ‘One corner of the work…defaced, but the other portions are fairly clear’.

Family disputes between John Hanmer Trevor and his mother, Elizabeth, led to a series of mortgages on the estate from the late 1720s. Eventually in 1741, John Hanmer Trevor disposed of the estate to one of the mortgagees, John Markham who was described of Paternoster Row, London. Markham died post-1756 and, in June 1761, his executors sold the Treflach estate to William James (d. 1775), a surgeon from Oswestry.