Plas Berw comprises a ruined medieval hall house (NPRN 15800) and a mansion of 1615, set on two sides of a forecourt or garden. It probably had walled gardens and was situated within a deer park (NPRN 265407). Notices of the site pre-date the existing buildings and the park may have earlier medieval origins, although there does not appear to have been an earlier house on the site.

The new house, built for Thomas Holland, is a two storey building with attics, with stone rubble walls under a slate gabled roof framed by tall end chimney stacks. It faces south-east onto the contemporary court where it had a five bay facade, the end, south-west bay being originally concealed by the old house. There is an off centre doorway below a heraldic panel with the date 1615. The windows are mullioned and transomed and the attics are lit by dormers. The court is entered by a dressed stone arch on the north-east, surmounted by a heraldic shield. The court was laid out as a garden, with an open central area framed by borders. At the rear of the house is a four stage tower rising to a pyramidal roof overtopping the rest of the house. The new house also had a central hall between a parlour and kitchen. Various extensions were made to the new house in the nineteenth century, including a block added at the south-west end when the old house had fallen into ruin. There are various outbuildings and farmbuildings, probably built in the 1820s-30s, including a coachhouse to the west of the mansion (NPRN 406286).

Sources: RCAHM Anglesey Inventory (1937), 100-102
Longley in Archaeologia Cambrensis 140 for 1990 (1991), 102-119
CADW Listed Buildings Database (5500, 5501)
Haslam, Orbach and Voelcker (2009), The Buildings of Wales: Gwynedd. Pevsner Architectural Guide, page 213.

John Wiles, RCAHMW, 25 July 2007