The blaze was reported shortly after 7:25 a.m. at 79 Miraflores Ave., and firefighters arrived at the home about five minutes later, San Rafael fire Battalion Chief Jeff Buscher said.
The fire went to a second alarm because the home was on top of a hill and could only be accessed by a narrow single-lane road, Buscher said. He said most of the firefighters had to walk up the road to get to the fire.
Firefighters controlled the blaze by 7:51 a.m., Buscher said.
The home's occupants awoke to the sound of the fire burning upstairs and escaped safely, Buscher said. No firefighters were injured.
The fire caused about $300,000 in damage to the home's structure and its contents, according to Buscher. The cause of the blaze is under investigation.
Buscher said the home apparently did not have a working smoke alarm, and that the incident serves as a reminder that people need to check that they have smoke detectors in their homes and that they are equipped with working batteries.