Plas Llandecwyn

Plas Llandecwyn is a small gentry house with a sub-medieval design, built in two storeys and featuring end chimneys. The structure is made of mortared rubble masonry and has a slate roof with tall gable stacks that include dripstones and capping; the northern gable stack is raised and hooded. The principal elevation faces west and consists of a long four-window range, with the openings generally offset to the right to accommodate a large principal fireplace at the northern end. The doorway is located to the right of centre and is flanked by 12-pane sash windows—one to the left and two to the right. Above, there are three 9-pane sash windows aligned in a row. The elevation steps up slightly to the left, featuring two wider 12-pane sashes on the ground floor, which have hood moulds that may indicate earlier openings, and a single 9-pane sash window above.

At the rear, service accommodation runs parallel to the main house and is roofed as an outshut. This section includes a gabled dormer and inserted rooflights, with a tall stack towards the southwest end serving a fireplace. A glazed roof has been added for a conservatory at the northeast corner of this range. The southwest gable has a doorway leading to the kitchen on the right, with a small 6-paned window to the left and a larger 6-pane horned sash window to the right. There is also a small-paned casement window in a partially blocked doorway at the far right.

The house is arranged with an entrance hall that leads to a heated parlour on the right and a main hall with a fireplace and stair on the left. The service accommodation is located in the parallel range at the rear. The entrance hall previously had partitions on either side, but only the upright timbers of the parlour partition remain. The hall features a large inglenook fireplace with a chamfered bressumer and a chimney stair alongside. The parlour has a smaller fireplace with a chamfered stone bressumer, while the kitchen fireplace has a plain stone bressumer.