Crews from Stanground and Dogsthorpe were called to a fire in a single-storey stable in Katherine Way.
Firefighters wearing breathing apparatus used two hose reel jets to extinguish the fire in the stable, which contained scrap wood.
They returned to their stations by 2.13pm.
Cause of the fire was deliberate.
Anyone with information should contact police on 101 or call Crimestoppers anonymously on 0800 555 111.