North Yorkshire Fire and Rescue Service and North Yorkshire Police are investigating after the incident on Whitcliffe Lane this morning at 8am (Monday, January 14).
A NYFRS spokesperson said: "The fire involved floorboards and joists and caused fire, heat and smoke damage to the room of origin. With some smoke damage to the rest of the building."
Firefighters will be carrying out a revisit this evening to check for hot spots, while North Yorkshire Police are appealing for witnesses to what is believed to be a case of arson 'due to the scale of the fire damage.'
The incident however remains under active investigation.
If you have information call 101, and quote log 80.