Barn approximately 10 metres to north-east of Alderthwaite Farmhouse

This is a large aisled barn, likely built in the late 15th to 16th centuries, with an aisle added early on. It was encased in stone during the late 17th or early 18th century and altered in the late 19th century, including the reconstruction of the northern truss. The barn is constructed of timber framing with thinly-coursed sandstone walling and has an asbestos roof.

The barn is single-storey and approximately two-and-a-half bays wide, with a single aisle on the eastern side. Large quoins are present. The west-facing farmyard side has inserted double doors with a wooden lintel on the right, and two rows of slit vents on the left. A later casement window is located beneath the eaves. The lean-to buildings at each end are of insignificant interest.

Inside, the southern end bay is paved with stone. This bay, and the adjacent central bay on the left, show late-medieval post-and-truss framing. However, a brick pier replaces a post in the south-east corner, and the tie beam on the far left does not sit on the adjacent wallposts. Long, curved braces extend from the tie beam and the arcade plate to the posts. Original and re-used timbers above the tie beam form principal-rafter trusses with double purlins and a ridge beam. Re-used rafters with halvings suggest the original roof was of collared-rafter form. The side aisle is thought to be an early addition, as its roof structure braces are lap-jointed rather than tenoned into the posts. The tie-beam of the northern truss incorporates a re-used timber and contains a row of small, empty mortices along its upper edge, potentially indicating that it was originally an external rail over a row of studs, possibly part of a demolished Elizabethan manor house. The barn was likely encased in stone around the time the adjacent cowhouse was built.

Alderthwaite Farm is believed to have medieval origins and formerly included an Elizabethan timber-framed manor house, which was demolished in 1878.