While returning from a from a first due working fire, the engine company was alerted to respond to company 18s area for a report of a building on fire. First arriving units had fire showing from the roof of a commercial warehouse. Engine 828B arrived 3rd due, secured a water supply and stretched a line over truck company 14 to the roof where the crew from 28 extinguished the fire. Crews operated for 4 hours before returning to service.