North-east Barn at Mostyn Hall Farm with adjoining stable range and flanking wall

The North-east Barn at Mostyn Hall Farm is a large barn built of random rubble and covered with a slate roof featuring coped gables. This long structure has near-central chamfered-arched high double doorways on both elevations. The yard elevation includes three high-set segmental-headed windows to the left of the central doorway and two tiers of blocked vents. To the right of the doorways, there is one similar window and additional vents. There are altered openings near the angle with the south-east range. On the garden elevation, the central doorway is flanked by high-set vents that have been blocked with brickwork.

At the rear of the barn, a length of wall connects it to Porth Mawr. This wall is made of rubble stone and features roll-moulded ashlar chevron copings. Adjoining the north-west gable of the barn is a late 19th-century low single-storey range that contains five stables built in blue brick with ashlar dressings. Each stable is expressed as a small advanced bay, complete with a boarded doorway and a small window beneath a coped gable.

The barn has been adapted for use as a grain store with drying equipment, but it retains an uninterrupted space of seven bays supported by queen-post trusses.