College Green House, like many Victorian buildings, combined both brick and stone in its construction. The bricks for the house probably came from one of the city’s brickworks. The sandstone was possibly brought in from Scrabo near Newtownards.
Unlike the terrace houses of McMaster Street, College Green House has a highly decorated exterior. It has carved stone panels in the dormers and above the doors, iron finials and a prominent bay window. Features such as these were a reflection of the wealth of the owner. Archibald McCollum was a rich merchant and could therefore afford elaborate decoration that would not have been available to the working classes.