The identity of the architect responsible for the Custom House of 1724 remains uncertain. Its design has been locally attributed to Sir Edward Lovett Pearce, however, it would be wise to heed Maurice Carig's advice 'to remain on guard against the temptation to attribute every Pearcean-looking building out of 1730 to the master himself'. The building is less robustly classical than Pearce's other known designs, for example Bellamont, Castletown, or Cashel Palace, - and the distinguishing feature of these houses- a distinctively Classical treatment of the roofline - is almost entirely absent from the Cork building, where there is no attempt to hide the steep slated roof. (Although it should be noted that in Charles Smiths description of the building in 1750, he mentions a 'cornice and balustrade at top'; however there is no signs of balustrade in the mid-nineteenth century drawing of the building by the architect Henry Hill). The architect of the Custom House could certainly produce work which was elegant enough, but his style was more formally rooted in an Anglo-Dutch red-brick tradition than in the high Palladian classicism of Pearce.
It is far more constructive to look to other early eighteenth-century houses in the Cork area for clues as to the architect of the Custom House; and in the seaport of Youghal, less than thirty miles from Cork city, a large house in the main street known as the 'Red House' provides solid grounds for comparison with the Cork building. The Red House, porbably so-called because brick buildings were comparatively rare in Munster up to the eighteenth century, was built by the Uniacke family in 1710. It has been traditionally ascribed to the Dutch architect and builder Leuventhen, and the design for the town house in Youghal contains key features which also appear on the Cork Custom House, such as the distinctive string course at first floor level, a gentle breakfront facade, quoins and window surrounds of carved limestone, and a lunette over the entrance doorway.
There is also in Youghal the famous clock gate straddling the main street, which although it bears the date 1771, was apparently modelled closedly on an earlier structure. Craig mentions Coltsman as a possilble architect for the clock gate, and compares it with the similar St.Ann's, the clock gate and the custom house are quite dumpy in appearance, and in spite of the classicising features of both buildings, they, and the Red House, share a homely feeling, and could possibly have originated from the same journeyman-builder's portfolio of designs.
In its original form the Cork Custom House was three storeys high and seven bays wide on both its main fronts. The northern facade, looking on to the River Lee, has a centre breakfront of three bays, while the eastern facade, wider and more ornate, has its five bays recessed, the centremost bay being flanked by engaged columns. Doric at ground level, Ionioc above, rising two storeys and surmounted by carved pineapples and a lunette. The pineapple motif was widley used as a symbol of hospitality in eighteenth-century European and American architecture, but it is particularly linked with Newport, Rhode Island, a seaport which prospered on the West Indian trade. Stone pineapples are found on several buildings n Cork dating from this period, and hint also at the close trading links which existed between Cork and the West Indies. The pineapples are carved of a particularly white limestone that is native to Cork. The engaged columns and lunette are also of this stone, as are the quoins and window surrounds. This contrasts pleasently with the red-brick facing of the building - although it should be noted that the entire building was refaced with new bricks when the 1884 extension was constructed, so that the old and new parts would match more closely. The centremost bay of this eastern facade, flanked by columns and other embellishments, appears to have been the original main entrance to the Custom House; however a window has been inserted at this point, again during the 1884 renovations.
The building was the Custom House for the properous port of Cork until the beginning of the nineteenth-century traces of its original function remain: the large Gallery at first floor level where the permanent collection now hangs was originally the 'Long Room' of the Custom House. This room would have been occupied by scriveners and clerks seated at long tables bearing ledger, where bills of lading would be prepared for ships sailing to and from Cork.
The earliest known description of the custom house appears in the book Voyages en Anglois et en Francois d'A. de la Motraye, en divers-es provinces..., published in 1732. Mortraye talks of the building and says it is 'the Handsomest of the public Edifaces & built after the Italian Manner'. some twenty years later, Charles Smith included a description of the building in his account of Cork:
"The Custom House is a large elegant building, of one main structure, and two returns; it consists of three stories; the angles, door-case, and window-frames, are of hewn stone, as is the cornice and balustrade at top; the other part of the building is of brick. In this house, are several offices of the management of the affairs of the excais and custome of this port; together with an elegant apartment, and all proper conviences for the collector, who resides in the house. On either side of the building are the store-houses, which form two handsome piazzas. Here is a good quay, furnished with cranes and other conveniences for the discharging of goods; and a new canal made almost quite around the Custome-house, so that several vessels may lie there at a time."
In the year 1724, the old Custom-house being too small, was taken down, and this elegant building was then begun to be erected, at the King's expense, which was finished the following year. there is a house standing in the Main-street, S. of the exchange, which was formerly used as a Custom-house; and on it, are the arms of England, with a ship, cut in stone, near the roof".