Fire and Rescue NSW (FRNSW) were called to the premises in Clarke Street just before 5am.
More than 10 trucks, including a ladder platform, and 50 firefighters arrived on scene to find the property well alight.
Crews quickly got to work to contain the fire but withdrew after the roof collapsed.
Firefighters continued to tackle the blaze from above using the ladder platform truck until it was contained about 40 minutes later.
The fire also caused damage to the property behind the smash repair.
There were no reported injuries and investigations are now underway into the cause of the blaze.
Smash repair business destroyed
A SMASH repair business in Guildford has been destroyed by an intense fire earlier today.