He practiced in Armagh , and then lived in Drogheda from 1786 before moving to Dublin about 1793 .
Johnston was born in Armagh , Ireland , son of William Johnston , also an architect , and studied architecture .
Johnston practiced in Armagh , and then lived in Drogheda from 1786 before moving to Dublin about 1793 .
Johnston was born in Armagh , Ireland , son of William Johnston , also an architect , and studied architecture .