Before and after graduating he worked for the following architectural firms: Rosman Hastings & Sorrel 1967, Burgess & Sprintz 1969, Bogle & Banfield 1972, and as a design assistant at Yuncken Freeman Architects (YFA)> 1972–1975.
At Yuncken Freeman he worked as a design assistant on the interior fit-out of the Austin Hospital new ward block under the eccentric but brilliant Tony Woodhouse.
The design also included some internal two storey spaces and floating stairs, following the firm's preferred Ludwig Mies van der Rohe model.
However his major architectural role was with the firm Perrott Lyon Timlock and Kesa, later Perrott Lyon Mathieson (1975-1981), as the project designer of the Museum Underground Railway Station fit-out (now Grand Central) and Melbourne Underground Loop Authority (MURLA) system graphics documentation, initially under PLM associate David Simpson.
Before forming his own heritage consulting practice and still working for the architecture and planning firm Perrott Lyon Mathieson, Butler completed one of the first heritage studies of the Melbourne Central Business District, undertaken for the newly created Historic Buildings Preservation Council, in the mid-1970s, and the City of Castlemaine Conservation Study.