Five fire engines were called to a carpet and home furnishing store in Preston city centre after a blaze broke out.
Firefighters were called to PC Carpets and Beds, on the corner of Lune Street and Fishergate, at around 6.20pm on Saturday.
Six officers wearing breathing apparatus entered the store to tackle the fire.
They used a jet, hose reel and an aerial ladder platform.
A Lancashire Fire and Rescue Service spokesman said the fire had been brought under control by 7.30pm.
The fire caused severe damage to a staircase enclosure on the ground, first and second floor, destroyed an external fire door and caused severe smoke damage to the first and second floors of the shop.
All of the stock was damaged by smoke.
No people were reported to be inside the building at the time of the incident.