Received report from Hopkinton Police for an outbuilding fire at #29 South Mill Street. Box 444 was struck and upon the arrival of L-6 the working structure fire was upgraded to a second alarm response. The occupant was made aware of the fire by a passerby knocking on his door. The initial size up revealed two (2) outbuildings, corn crib and storage shed heavily involved with fire with heavy fire extension to the "B" side and attic of a two story type 5 unprotected barn and two apartment residential property of approximately 7,145 sqare feet. Upon arrival C-2 established South Mill Street command, attack two, 200' 1 3/4" preconnect was assigned to the "B" side of the building to knock down the heavy exterior fire. Attack 1, with 200' of 2" hose advanced the the line across division 2 from the access door on the "A" side near the "D" corner. Attack 2 was moved to division two of the attached barn via the interior stairway on the "A" side near the "B" corner and attempted to knock down heavy fire on division two and in the attic of the barn. Engine 2 was instructed to supply a 4" supply from the dry hydrant at Blood's Pond to Engine 1. Upon arrival the Ashland Tower unit was placed on the "A" side of the fire and Engine 1 supplied a 4" supply line for the Tower Unit. Ashland personnel were assigned to assist on the attack 2 line on division two of the barn. The Tower Unit master stream was placed in service when the rear roof of the "C" side of the barn collapsed and the residential units were exposed to heavy fire conditions. Ashland Chief Kee was assigned the "C" side sector and the Southborough Chief was assigned as the accountability sector. The initial RIT assignment was the Southborough Engine company, after arrival of the Milford Engine company the Southborough personnel were reassigned to multiple positions on Division 2. The station coverage Westborough Engine was requested to the fire and assigned as the RIT component allowing Milford personnel to be rotated into the Division 2 area with a second 2" line for additional knockdown and overhaul. The fire was placed under control at 1535 hours. Extensive overhaul was required and a fire detail consisting of two personnel and T-1 was held in place until 2000 hours.