It may be that the 18th century barn became ruinous and was rebuilt by Mr Heaven after 1838. His agent, Mr Malbon, does in fact refer to a new barn in 1839.
The present Barn is constructed of granite and was converted to a threshing house when the round house was added. This provided a circular walk for a horse or donkey, harnessed to a gin to provide motive-power for the machinery in the adjacent threshing room. Later when engines replaced animal and man-power, the Barn housed one of the few mechanical contrivances on the island: the ancient 4½ horsepower Blackstone stationary engine. It ran on paraffin and powered the threshing box, chaff-cutter, grist-mill, circular saw and subsequently a sheep-shearing machine for which purpose it never really had sufficient speed.
On October 4th 1944 Lundy suffered a violent gale and the roof of the Barn was lifted off in one piece, falling near the entrance to the stables and the dung heap.
In 1975 when Landmark began work on its restoration, the Barn was all but a ruin. The roof was replaced and all the outer rendering removed to reveal fine granite coursing beneath. Originally it was planned to convert the Barn into a museum, but this scheme was abandoned and it became instead a hostel for 14 people.
'The work of conversion had been very cleverly and distinctively carried out, mainly by men employed on the island, but with the assistance of an expert tiler, and an expert carpenter, Mr Alan Walker. Mr Grainger (Mr Gade's successor as agent) invited me to declare the new Barn open on August 24th, 1975, and I consented, perhaps nostalgically, having such long memories of all the work which had been carried out there when it was a farm building: threshing, chaff-cutting, cake-crushing, sawing timber, grinding oats, shearing, and I must not forget to mention, the strenuous work of starting the old Blackstone oil engine.'
'There was a strong westerly wind blowing, and so we made the opening ceremony brief. Ian Grainger offered me the key, I unlocked the door, and he and I entered together. I must say the metamorphosis was very striking: the walls were covered in varnished white pine and the floor tiled. The beds arranged in a semi-circle in the Round House looked comfortable and attractive with their purple blankets, and it seemed to me that there was a surprising amount of light in the Barn from three quite small windows. The first tenants, who were a party organised by the Lundy Field Society, moved in the same day.'