The 69-year-old woman didn't need hospitalization after the Wednesday afternoon incident in the Sacramento suburb of Rosemont.
The Sacramento Bee ( http://sacb.ee/11ZYTQV) says her 24-year-old grandson, Donald Eugene Evans, is in jail without bail.
He was booked for investigation of arson, assault, elder abuse and threats of violence as well as a probation violation.
Sheriff's investigators say Evans and his grandmother were arguing when Evans struck her and set fire to the home. The nature of the dispute hasn't been disclosed.
Sacramento firefighters extinguished the flames. There is no damage estimate, but the home is uninhabitable.
Information from: The Sacramento Bee, http://www.sacbee.com