Work will begin in April to strengthen the Radio House building on Church St after further structural assessments found the building poses a high risk in an earthquake.
Lands Trust Masterton said preliminary assessments were made of all trust buildings last year, which showed the two-storey building in Church St met more than the minimum requirement of 33 per cent of the new building standard and was classified as "moderate risk".
However, following the evaluation of the original design engineer's building plans in Wellington and a more detailed structural assessment Radio House has been reclassified as "high risk".
"This highlights the importance of following initial structural assessments up with detailed ones, which in this case has shown that the building is not as safe as we thought it was," Lands Trust Masterton chairman Alan Sadler said. "We are working through detailed assessments for all of our buildings that were initially assessed at between 33 and 67 per cent."
Buildings classified as high risk or "earthquake prone" do not comply with the seismic performance standard for new buildings (less than 33 per cent) and are also a significant risk to life in the event of a moderate quake. The Radio House building was found to meet just under 33 per cent of the new building standard.
The trust has already demolished three high-risk buildings including the former Opera House at 27 Lincoln Rd, and the Elliot Building and former St Patrick's School building both on Queen St.
"At this time there is no requirement on us to do anything and the local body does not require anything," Mr Sadler said.
"We're being proactive with these buildings and carrying out completely necessary repairs to bring them up to the necessary standard. We're ensuring that our tenants and customers are being looked after."
The strengthening work will bring Radio House up to 100 per cent of the new building standard. Bracing walls will be installed at either end of the building and wall and ceiling bracing added through the lower floor. The cost will be known once the detailed design is complete.
"We have met with and briefed the Radio House tenants and will work with each of them to minimise business disruption when the work gets under way. Because all work will be on the ground-floor level, there will be little or no impact on the upper-floor tenants," Mr Sadler said. "Our tenants understand the situation and have a range of options including temporary relocation or closing for a few weeks. Work will be scheduled in stages to minimise disruption for each of the five affected tenants."
The trust refurbished Radio House in 2009, before the Christchurch earthquakes and the initial assessments of all trust buildings in 2011.