Engine 503 was dispatched for a report of heavy fire showing from a vacant house on Sharon Road in Dumfries-Triangle, VA. Upon arrival the home was fully involved and was determined by the on duty Battalion Chief that we would proceed with a defensive exterior attack. Engine 503 worked quickly to get a knock on the fire with the help of Engine 523 and Engine 510. After the fire was out Engine 503 remained on scene to assist the Fire Marshal.