4a, St Marys Square

4A St Mary's Square is a house and office built in 1811 or 1812, originally serving as a Methodist Chapel. After 1878, it was repurposed for a stay manufactory and later used for both commercial and domestic purposes. The building is constructed of red brick and features a fully hipped pantiled roof with a wide paired modillion eaves soffit.

The exterior is two storeys high with a three-window range on the south front, showcasing small-paned sashes with semicircular heads, radiating glazing bars, plain reveals, and gauged brick arches. A large central entrance from the 20th century includes paired pilasters and a heavy cornice hood, leading to glazed double doors. The east front has an upper row of three small-paned sashes in plain reveals with flat gauged arches. A lean-to structure was added to the rear after 1878, which contains the stair to the upper storey and incorporates part of the east garden wall of No. 4. A plaque on this wall reads, "This wall belongs to (name illegible) 1827."

Inside, there are two rows of reused 17th-century timber posts that support the upper floor, which were inserted after the building stopped being used as a chapel. On the upper storey, the north wall has two former window openings with semicircular heads; one is blocked while the other has been converted into a doorway.