4 Tan y Bwlch

Nos 3 and 4 Tan y Bwlch in Llandygai are a pair of single-storey cottages built for quarry workers. Each cottage has a two-room layout with a loft and is oriented from northwest to southeast. The exterior features roughly coursed and dressed rubblestone blocks that are rendered and painted on the gable ends, topped with a slate roof. Each cottage includes three-light windows with slate sills on either side of a slightly offset entrance, along with integral end stacks and a shared ridge stack located centrally between the two cottages. There are also windows on the gable ends that light the lofts and catslide lean-tos at the rear.

The cottages have undergone some changes, including 20th-century windows flanking a 20th-century panelled door with an integral fanlight. One of the integral end stacks has been removed, and there is a large 20th-century extension at the rear. The original gabled slate ogee-arched porch remains, with a 20th-century half-glazed door beneath it and two 20th-century rooflights to the right. The interior was not inspected during the survey.