Crews were called to Sponge N’ Hoses on Muir Street just after 5.35am on Wednesday.
A Scottish Fire and Rescue Service spokeswoman described the premises as “well alight”.
Four appliances were in attendance, including two pump vehicles and two aerial vehicles.
It is believed no one was in the property when it went up in flames.
The surrounding area has been cordoned off by emergency services.
Some public transport has been impacted by the incident.