Two appliances and crews from Aylesbury, one from Thame and one from Wheatley attended, along with two officers.
The first and second floor of the building were affected by smoke logging. A commercial unit on the ground floor was evacuated.
The firefighters used four sets of breathing apparatus, two hose reel jets and a thermal imaging camera.
The fire was located in an expansion joint in the stairwell cavity between the ground and first floor. The firefighters used two fog spikes, a short extension ladder and small gear to access the seat of the fire.