A water flow alarm went off just before 6:45 p.m. Saturday at 1 Wind Stone Drive, according to Madison Fire Department.
Firefighters reported discovering a fire sprinkler going off on a four-floor deck when they arrived, as well as a fire on deck directly below.
A deck chair and siding to the building were damaged in the fire, MFD said.
Crews believe a cigarette not properly thrown away was to blame for the fire.
Firefighters credited the sprinkler for putting the fire out quickly. No one was displaced.