The $70 million call to demolish and rebuild Tauranga city centre is expected to be made today.

Councillors have a transparent trail showing the figures and reasoning leading to today's decision.

They are using a treasury programme, a business case decision making toolbox which lays out the option costs and benefits of the various ways of dealing with a mouldy and leaking central city administration block.

A perspective of the possible future view across Willow Street.

The report shows renovating will cost more than the completed buildings will be worth.

The estimate on the worst affected administration block is that it will cost about $10 million at a cost of about $3,719m2. Total costs of the project are estimated at $13.7 million, leaving the city with a building having a market value of $6.5m.

A new building on site that is built and owned by Council offers better value for money and is therefore the recommended ‘preferred way forward', according to the report.

The option is used for analysis of the three short-listed masterplan options described later in the Economic Case. According to the financial case, a ‘build and own' option may not be affordable.

The Commercial Case retains both options as well as a combination of those options as viable commercial options, which will be more fully analysed during the consideration of a procurement approach for the project.

The existing buildings' floorplans and inter-floor and building access are not suitable for an Activity Based Workplace.

Activity-Based Workplace (ABW) is the label given to workplaces that have no or few assigned workstations. Instead, a landscape of different places to work is provided, with the aim that each different setting is conducive to particular tasks.

The overall number of work settings can be reduced, as a workstation becomes a shared facility, just like a meeting room – neither is used all day every day by everyone. Therefore, when contemplating a new work environment, many organisations consider if ABW could potentially work for them.

It means less space is needed for the 400 council staff, which means a smaller cheaper building to house the same number.

The report states an ABW city council workforce will take up 8,170m2 compared with 12,696m2 for the conventional office space. The price difference is $63m compared with $95m.

Organisations that have adopted ABW workplace designs report productivity gains of 6 to 16 per cent annual productivity gain. A 30-40 per cent reduction in work related sick days and a 10-50 per cent reduction in staff turnover.

The demolition of the existing buildings on the site prior to longer term decision on the future of the sites will mean that Council will create transitional open spaces in these areas until a longer term future is decided.

The decision today is just on delivering a new civic administrative building with surrounding open space on the 91 Willow Street site, and delivering a civic square on Masonic Park

Investigating the feasibility of a potential civic precinct based library, museum and performance venue, is further work.

The council role in each of these may be different, says the report. For example council may lead on providing the library, facilitate a hotel development and own or tenant an office building. The next stage of the project will provide further evidence to support any role in the delivery of each of the elements.