It appears the blaze started in a narrow yard space between the Fremaults' home and that of their neighbors, Santa Rosa Fire Capt. Jack Thomas said. At least six people were displaced.
The cause of the fire is still under investigation.
Once started, the flames spread rapidly.
"It was moving extremely fast, but crews got on it extremely fast," Thomas said. The fire was reported at 1:19 p.m. and when units arrived shortly afterwards, there were heavy flames in between the two houses and fire had spread to the roof of the Fremaults' two-story home.
Firefighters were able to knock down the worst of the flames in 30 minutes, Thomas said. The remaining hotspots were under control within about an hour.
In all, nine engine companies, two truck companies, one ground support unit, three chief officers, one staff officer, an ambulance, and two fire investigators responded. In addition to Santa Rosa firefighters, Cal Fire and Rincon Valley responded, as well as Santa Rosa Police and Sonoma Life Support.
Thomas estimated damage to both residences at $250,000 and $50,000 to belongings.
The right side of one home and the left side of the other were blackened as fire crews cleaned up Thursday afternoon. A portion of the Fremaults' attic was burned through to the rafters and a tree in their front yard was scorched.
Carol and Bob Fremault, who lived in their home for about 30 years and raised their children there, appeared to take the loss in stride.
"Nobody was hurt," Carol Fremault said. She added, "I don't know what we would have done without the neighbors here."