Two appliances and crews from Aylesbury attended.
The small fire was out when they arrived. There was around five per cent fire damage on the third floor of the building.
Thames Valley Police were notified of the incident.
One appliance and crew from West Ashland and one from Broughton attended. The fire was on the ground floor and is believed to have been started deliberately. Firefighters used buckets of water.
Three appliances and crews from Aylesbury attended. Firefighters used three hose reels, one set of breathing apparatus and a water tanker.