Lord Sondes the Earl of Faversham acquired Standard Key in 1677, at a time when the port-trade was expanding. At the same time additional warehousing was built from timber and stones taken out of the Abbey ruins. Gillets warehouse, formally known as Provender Mill is a timber framed building of considerable length. (49m by 6.5m). It can be divided into three distinct building phases, the main range, the chamber block and the Victorian bay. The main range is 12 bays long and divided into 2 lofts of 6 bays each, the form of construction indicates a 17th century date. The chamber block is a three bay building with a steeper pitched roof. The wall timbers are in staggered panels and the brick infill is used decoratively. The timbers used in the chamber block are of a size and quality that indicate they would have originated in the Frater building of the Abbey .
In the Watson Collection of Sondes papers at Rockingham Castle is the original estimate and plan for rebuilding the warehouses on Standard Key, dating from the late 17th century. The builder had annotated the plan and section of the new warehouse as follows: “Sir, this is a plan and section of the store houses at the Standard Key if they be all joined together as you purposed: with the same length each tenant has now as I have mentioned on the plan.” The three tenants named on the plan are Stephen Jones who has four bays, John Gould and Thomas Raynor who both have two bays. Stephen Jones was Mayor of Faversham in 1698 and his grandson Stephen Jones held the same office in 1773. On Edward Jacobs’ 1745 map of the town the warehouses are shown ‘joined up’. It is likely that a pivotal point for construction from separate warehouses to one complete unit would be late 17th or early 18th century.