They’re old, outdated, and with around a quarter empty, the C Grade office stock in Perth’s CBD is ripe for conversion, according to new research commissioned by the City of Perth.

The research was undertaken by architects Cameron Chisholm Nicol, Wood and Grieve Engineers and property market consultancy Y Research.

Currently about 60 per cent of Perth’s office space comprises C Grade buildings that are generally over 20 years old and showing wear and tear.

A current vacancy rate in this tranche of properties of 25.7 per cent means there is around 340,000 square metres of vacant space across metropolitan Perth, according to Y Research data.

Six potential uses for the buildings have been identified. They include refurbishing to A Grade standard, conversion to multi-residential, conversion to student accommodation, conversion into vertical schools, conversion to mixed-use, and conversion to health and wellbeing uses.

The research team looked at the specific requirements for each typology, benefits and constraints and costs.

The next step for council is its economic development team will be holding workshops and consultations with building owners over the next five to six weeks, a City of Perth spokesman said.

Perth lord mayor Lisa Scaffidi told WA Today the designs came with comprehensive analysis, design and technical information to kickstart any private sector effort to overhaul them.

“With developments such as the new Perth Stadium, Yagan Square, Perth City Link and Elizabeth Quay currently underway, there is no better time to think creatively around the role the City’s existing building stock can play in shaping Perth’s exciting future,” Ms Scaffidi said.

“While the adaptability study can’t provide a solution for office vacancy (which has been largely brought on by macro-economic conditions), it generates a conversation within the industry and imagines thought-provoking concept schemes to improve the diversity and resilience of Perth City.”

Wood and Grieve Engineering’s contribution to the research and designs included expertise on hydraulics, mechanical services, fire engineering, structural engineering, electrical engineering and sustainability.

WGE Perth associate and sustainability project engineer Phillip Cook said the reuse of existing spaces presented challenges that require innovative solutions.

“There are significant environmental, social and economic benefits of making better use of under utilised spaces to ensure the built environment continues to meet our current and future needs,” Mr Cook said.

In a blog post about the project, Y Research principal Damien Stone said the idea of adaptive re-use already had precedent in the city.

Both the Duxton Hotel and the Rydges Hotel are conversions of commercial offices, and an office building at 50 William St became a vertical Anglican High School.

Currently, a former Telstra office building in Northbridge is being converted to student accommodation, and another office property also in Northbridge is being converted into a hotel.

Mr Stone said it was understood there were also a number of other commercial buildings looking to convert to multi-residential apartments when current leases expire.

He said the ultimate driver of building conversions would be market acceptance from potential occupiers, and market pricing that reflects the cost of converting buildings.