As Engine 432 and Truck 403 were clearing from a walk through at George Mason units were alerted to the box alarm on San Juan Drive.  Truck 403 arrived to find a two story split level home with fire showing from the lower level.  Engine 432 arrived seconds behind the Truck and stretched a line.  The Rescue Engine picked up their line as they arrived as the second due.  Units make quick work of the fire keeping the fire confined to the lower level.  Another house saved by an aggressive interior attack.  Battalion 443 (Ahrens) had San Juan Command.