The smoke detector warned the family of the flames at the two-story house at 190 Shooting Star Isle around 6:30 p.m., so they called 911 and safely evacuated, Battalion Chief Jim Scott said.
The blaze traveled from the garage through a pipe that led to the attic, Scott said.
Six agencies and more than 40 emergency personnel responded to help extinguish it.
By 7 p.m., the fire was contained.
Scott said it appeared to have been accidental but did not know exactly what caused the fire.