"We searched the council records and discovered when it was built [1979], but not who designed it," Cousins said.

Fortunately, when Cousins moved into the building less than a year ago, only cosmetic changes had been made. Rudimentary partitions dissected many of the offices, a number of which were medical services, allied to the hospitals nearby.

So when the architects moved in, along with the Maben Group, a commercial construction company that occupies the same level, less, rather than more, was the mantra from the outset.

And in some instances, the process was stripping away rather than adding.

"It's a fine example of brutalism. The materials, particularly the off-form concrete, have been beautifully conceived," said Cousins, who occupies about 120 square metres of the second level.

While the 1980s partitions were relatively easy to remove, the mustard-coloured render on the building's facade required considerably more effort. With the render removed, the building presented a striking form to the street.

The interior was also handled with "kid gloves". Apart from opening up rear windows and doors to an existing eastern terrace and inserting steel handrails to meet building standards, the shell is virtually intact.

One of the decisions made by Cousins from the outset was to avoid any more partitions than needed. The two occupants share a communal kitchen, with a large pivotal door separating the two.

"We both have our own entry, but it wouldn't be an efficient use of space to include two kitchens," Cousins said.

However, new spaces have been "carved" into the sculptural building. There's a separate area for workstations, delineated by plywood joinery. And there's also a fully enclosed archival/meeting room.

To minimise disruption, as well as keeping to a budget, the amenities were left in their original positions, lightly reworked. Carpet tiles on the floor were removed, allowing the concrete floor to be polished and reveal its aggregates.

The ceiling tiles were also taken away, and replaced with plywood. And to increase natural light, skylights were inserted above the work areas.

"We've used a limited palette of materials. It's either concrete or plywood," said Cousins, who has used plywood extensively in several of her smaller projects, such as in homes and apartments.

"Plywood is a light counterpart to the concrete, but it's also an economical materials, particularly if it's left unfinished."

But rather than simply using plywood as an inexpensive material, it's been treated as a design feature, with shadow lines separating the walls from the ceiling.

Although Cousins didn't want to mimic the 1970s, she was respectful of the period. Apart from cosmetic additions, such as '70s-style tracklight fittings and plastic door handles, there's a new concrete block plinth-like wall on the terrace, complete with built-in containers to support pot plants.

Likewise, a limed timber was used for the deck on the terrace, evocative of many of the outdoor areas from this period.

"I wanted to be as reductive as possible, without impinging on the original design," she said. "Since moving into this space, there's been a positive effect for both staff and clients.

"This space has a powerful effect on one's mood. We feel extremely fortunate to be working here."