Firefighters responded to the store at 2052 Redwood Highway at 4:45 p.m. and discovered a fire in a parapet on the roof, Larkspur Fire Chief Robert Sinnott said.
The fire was quickly extinguished, and the flames were contained to a small section of the roof, Sinnott said. The damage was estimated at $25,000.
Crews installed plastic sheeting to protect the damaged part of the roof from the weather, Sinnott said.
Fire crews from Kentfield, Ross Valley and San Rafael also responded to the blaze.