PLANS for a lean-to extension that would have covered an arrow slit vent on an 18th century thrashing barn have been refused on appeal.

An application for planning permission and listed building consent was made to Monmouthshire County Council to allow open access from a kitchen, in the barn that was converted to a home in either the late 1990s or early 2000s, to the proposed single storey extension.

But that was rejected by the council’s planning department in January and the decision has been upheld by an independent planning inspector following an appeal to Planning and Environment Decisions Wales.

The inspector, identified only as JP Tudor, said they agreed covering the arrow slit vent would have an adverse effect on the significance of the home, which is an associated building of the grade II-listed farmhouse at Llanfair Kilgeddin.

The farm was listed in 1991 for its architectural and historical importance as a substantial early 17th century house while the barn, now in separate ownership, is considered to retain “significance as an example of a substantial former agricultural threshing barn, possibly dating from the 18th century”.

The council had said a lean-to could be acceptable but the one proposed would involve the unacceptable removal of a large part of the rear external wall to create the opening from the kitchen.

Tudor’s report stated: “That would entail the loss of one of two arrow slit vents within that section of the wall.”

The applicant said the timber frame extension would be sympathetic to the original building and a modern window added during the original conversion would also have been removed while the arrow slits had been rebuilt in a non-traditional square-sided manner.

The inspector upheld the council’s decisions and also noted Welsh historic buildings body Cadw had “appeared” to object to the lean-to extension and ancillary works, as well as the proposed opening, but said those elements had been approved in a further application made in January with a smaller proposed opening to the extension.