The Long Barn, Vynol Old Hall, is of two 17th century phases. The first in 1605, and the second in the 1660's when it was extended to the west. It is 42m long and 9m wide, making it possibly the largest intact barn of this date in Wales.
The barn is of 10 bays and dovecote; it has large slates and thick, slightly battered walls having off-centre cambered headed doorways both sides, and 2 tiers of slit ventilators. The north-east gable has a 2-light stone mullioned window, opening to an internal dovecote. The early date stone is placed over the doors.
Internally it retains the largely original roof structure, comprising tie and collar beam trusses with lapped vertical struts and 3 tiers of purlins. There is a stone flagged floor to the barn, and timber lintels over the wall vents. It is storeyed beyond the full height stone wall at the south-west end, with roughly hewn ceiling beams and some cylindrical piers. A fine staircase rises to the 4-bay attic, echoing the main stair of Vaynol Old Hall, having turned balusters and pronounced newel finials; it is probably assembled from redundant parts of that staircase after it was moved in the late 17th century remodelling of the Old Hall.
The fine cupola was probably added in 1899, the date the clock was installed.
