Bryngwyn was built in 1773-4 for William Mostyn to the designs of Robert Mylne (1733-1811). It is a simple classical 2-storey red brick country house with freestone dressings, a hipped tiled roof, and various brick chimney stacks. The house was partially rebuilt circa 1813, following a fire in 1793.

The original Mylne house has Flemish bond brick, but the later work is in English garden-wall bond. A symmetrical 5-bay entrance front to west relates to the 1813 work except for the pediment which was added recently as a reference back to the original Mylne design. The central 3 bays are advanced beneath the pediment, which has ball finials and a circular attic window, and freestone dressings. The central panelled door has a leaded fanlight and pedimented doorcase.

Stepped down and set back to the left is the service range which has further small-paned windows and a hipped slate roof.

The symmetrical garden front is especially characteristic of Mylne's style epitomising what Colvin calls his 'fastidious restraint'. It is of 5 bays including a splayed bay to centre where the 'splays' are unusually recessed and the outer bays are very slightly set back.

The main public rooms on the east side retain Mylne's interiors. In the centre of the house is a fine open-well staircase, top-lit by an octagonal lantern; it has a turned newel with cast iron upright but is otherwise understated in character, but rises to a spacious landing with four Doric columns.

There are whitewashed cellars with four barrel-vaulted chambers and a deep well.

Reference: Cadw listed buildings database.