Three linked appeals relating to Stable Cottage in Wheatsheaf Lane, Woodmancoat,, near Henfield, have been dismissed.
Appeals inspector Michael Hetherington ruled they would adversly affect the character of the area. with significantly increased residential use in the first two.
Original applications by Mr and Mrs B Stern had been refused permission by Horsham District Council. One was for change of use from agricultural and workshop to residential, and from personal storage in another area to residential use.
The second appeal related to windows, a new door and replacement rooflights to an existing barn. The third was for a non-listed building to provide floors, storage areas, washing facilities and heating system.
Mr Hetherington said it was clear that both floors in the latter were already in residential use.