Russ Buller, director of emergency services for Hesston, said volunteer firefighters found heavy smoke coming from a 100-by-200-foot metal building at Kropf Lumber when they responded to the 3:24 a.m. alarm.
When firefighters got inside, they found stacks of wood and other building supplies in flames, Buller said.
He said more than 50 firefighters from Hesston, Newton and Moundridge were able to keep flames from spreading to the showroom.
An excavator operator tore out a front section of the building and dragged lumber out of the fire, robbing it of fuel.
Firefighters also peeled off a corner of the roof and punched holes in it to vent heat and smoke out of the building.
The fire's heat was strong enough to warp and twist the steel frame and siding, and it melted a firefighter's visor.
Buller said a cause and damage estimate were not available.
Kropf Lumber was destroyed by a tornado in 1990. The owners rebuilt and reopened in 1992.