Church of England was anticipated. "Habit had accustomed [congregations] to the[ir] existing places of worship" by the time it became clear that Unitarianism would be a separate denomination, "and the domestic influence thus established by association made itself felt" in subsequent chapel architecture. The Horsham chapel is a "plain, cottage-like building" which forms part of a group of old vernacular buildings on the west side of the Worthing Road—including Horsham's Quaker Friends Meeting House. It has walls of red and blue-grey brick, two storeys and a hipped roof (with a hidden central depression) laid with Horsham Stone tiles. The main façade faces east, and sits on a brickwork plinth with a stone course. A similar band separates the lower and upper storeys. The date of construction is etched in one of the casement windows. The central porch dates from the late 19th century. The rear (west) wall is obscured but retains its original ground-floor paired arched windows and first-floor gallery windows. The north and south walls have single-window ranges; those on the south side are hidden behind the baptistery and vestry built in 1772. These are in the form of a lean-to with a sloping tiled and gabled roof and an arched window. Writing in 1914, one architect stated that "to a casual glance, the chapel ... might very well be a detached private house". The chapel's interior dimensions are . Two timber columns of the Doric order, with square bases and decorative capitals, support the roof, which is plastered. A panelled gallery at the north end is held on an octagonal column and retains its original box pews; a matching gallery was removed from the south side during the 19th-century renovations. The original rostrum stood between the two arched windows on the rear (west) wall. The southern extension has two vestries flanking a brick-lined, floor-set baptistery with stone steps. It was fed by a well sunk in the floor of one of the adjacent rooms. The "fine interior" also has monuments to John Dendy (one of the founders) and family members, members of the Gatford family and the Rev. Robert Ashdowne, minister between 1831 and 1861. In the graveyard, an ornate table-tomb to Richard Browne has gadrooning and fluting. The chapel is set a long way back from the street within its graveyard. At the time of its construction, mistrust of Christian denominations outside the Established (Anglican) Church was