Threshing Barn at Tre-castell Farm

The Threshing Barn at Tre-castell Farm is a large agricultural building dating from the 19th century. It features an open east side supported by four tall cast-iron columns, with stone walls made of local limestone masonry that are uncoursed, and a slated roof. The main roof is divided into four bays, with hipped end bays; the northern end bay is two storeys high and separated by a stone cross-wall, while the space beneath the four common bays and the southern end bay remains unobstructed.

The northern elevation is symmetrical, showcasing two storeys and two windows. It has centrally aligned doors above and below; the upper door is semi-glazed and functions as a window, while the lower door includes an overlight. Both levels feature four-pane sash windows. The southern elevation is more plain but includes slits for ventilation or for the power drive.

On the western side, there is a lower range of buildings that have been converted for domestic use. This range has a slate roof that continues the slope of the barn roof, featuring one large gable and three smaller gables, along with an additional gable on the northern flank. There are three doors and five windows below, with one window in each gable above; all windows are sash type with four panes.

The barn's trusses are of superior design, incorporating a mix of timber and wrought iron. They include a timber collar beam and struts, an iron king tie, and iron ties connecting to the feet of the rafters.