A mother and daughter were home but escaped without injury, along with their pet. The male resident wasn't home at the time, said Fire Marshall Rick Terry of the San Ramon Valley Fire Protection District.
The woman called in the fire from a neighbor's house. Shortly afterward, five engines, two trucks and a paramedic arrived on the scene to find heavy smoke coming from the garage, fire officials said.
The firefighting efforts were complicated by several layers of roofing material atop the house.
"The roof appears to have been re-roofed up to three times," Terry said. Two layers of wood shake shingles were covered by sheets of metal roofing material.
Firefighters on ladders had to peel away the metal covering and chop through the wood shingles to ventilate the roof and quell the trapped flames.
It took about an hour to contain the fire, estimated Terry. Some smoke filled the rest of the house, but the fire did not spread into it. The house sustained around $150,000 of damages including to the ceiling and roof while fighting the fire.
Rodents have been known to enter homes via roof vents and dwell in the attic. They can chew away at the installation, causing the wires to come in contact with one another and generate heat, Terry explained. Clothing and other combustible materials stored in the space can increase the risk of fire.