Fairfax County Fire and Rescue Department units responded to the fire at 1274 Vintage Place about 2:30 p.m.
Firefighters encountered smoke coming from three sides of the end unit, and fire in the basement of the two-story townhouse upon arrival, FCFD said.
The fire was brought under control in about 20 minutes. There was extensive damage in the basement, laundry room, and to the ceiling and flooring above.
Firefighters said an upstairs smoke alarm alerted the lone occupant, who escaped unharmed. Two residents have been displaced and the American Red Cross is providing support.
Damage is estimated at $150,000.
Fire investigators said the fire originated in the basement laundry room. The cause of the fire is undetermined as an ignition source was not found.