The following text is from the original listed building designation:
1. 5275 UPPER STRAND STREET (North Side)
Nos 19 and 21 TR 3358 1/181 19.5.50. TR 3358 1/181A
II GV
2. At one time made into 2 cottages, but now one house as originally. C16 timber framed house, refronted with red brick in the C18 facing Upper Strand Street, but timbering showing in Quay Lane on 1st floor, with curved braces overhanging on bressummer and brick brackets. Sash windows inserted, those on the ground floor with cambered head linings. Glazing bars intact. 2 doorways and small flat hoods over. 2 storeys, 2 windows facing Upper Strand Street, and one window facing Quay Lane. The interior has 2 C16 plaster ceilings and a painted plaster coat of arms over the fireplace on the ground floor, but the panelling and original staircase removed. At corner of No 19. A gas lamp of mid C19 date upon a bracket. Square plan lantern larger at top than at bottom with sloping roof, terminating in a bell shaped vent and scalloped cap and finial over.
Nos 13 to 25 (odd) form a group.
Listing NGR: TR3326558158

Description from record TR 35 NW 239:
The main part of the house dates back to the second half of the 15th century. It is a three bay building which had a small open hall set between storeyed end bays. Cellars under the whole range may be early but are more likely to date to the 17th century. Between 1603 and 1625 the house was remodelled and extended at the rear, and was updated by the addition of elaborate plaster ceilings, moulded doorways, a good staircase and painting and panelling. There is some uncertainty about the layout and extent of the property at the time, and it is unknown who commissioned the new work. By the late 18th C it had been divided into two, the parts only being reunited earlier this century and the timber framing refronted with red brick. It is unclear why or when the house received the name The Old Custom House. (1)

English Heritage, List of Buildings of Special Architectural or Historic Interest (Map). SKE16160.

<1> Sarah Pearson, 1998, The Old Custom House, Sandwich (Unpublished document). SKE7680.