tony just looked at the link you kindly sent me and i found reference to sinclair carroll relating to the proposals, estimates and specifications for the primate's palace, armagh. it says the architect was william farrell and the buuilder was sinclair carroll - this was march 1826. in slater's commercial directory of ireland 1846 sinclair carroll is listed as builder, architect and valuator living at beresford row, armagh, so obviously between 1826 when the primate's palace was built and 1846 he had progressed to being an architect. i also know that he was responsible for building both newry and armagh workhouses in 1839 and 1840, so he must have been working his way up in the building world.
cheers cesca