Walker was working on the centre, which has been closed while undergoing repairs for damage caused by an earthquake.
He climbed through a fence that was around the construction site and gained entry to the building by climbing a scaffold at the front of the building.
That took him to a window and he got inside the building. He cut various cables and used a ladder to climb into a large ducting unit. He used this to gain access to a room containing the air conditioning equipment for the building.
Once inside that room, Walker caused considerable damage by cutting cables and taking doors off switchboards.
Walker denied the burglary charge but was convicted following a judge-alone trial in the Rotorua District Court in July this year.
His offending was discovered after police found a fingerprint inside an electrical box in the air conditioning room and Judge Glen Marshall, who heard the trial, considered there was no credible explanation for the fingerprint to be there and therefore must have been left during the burglary.
The High Court decision said the specific amount of damage couldn't be quantified but there was considerable delay in finishing the remedial work because of the need to repair the damage caused.
The head contractor also had to employ increased security at the site.
Lawyer Alister Burns, who represented Walker, said in his appeal arguments home detention ought to have been considered given Walker was a low-risk re-offender and was low-risk to harm others. He had also complied with his electronic-monitoring bail which meant he was likely to comply with the conditions of a sentence of home detention.
Justice Lang said in his decision he wouldn't grant home detention as a deterrent message needed to be sent about "wreaking havoc" in damaging the equipment and operation of the centre for the sake of not a lot of money for scrap metal.
"As the judge pointed out, Mr Walker's offending involved several aggravating features. It was obviously pre-meditated and resulted in considerable damage and financial loss. It also involved elements of breach of trust," Justice Lang said in his decision.
Council organisational enablement deputy chief executive Thomas Colle said the $300,000 was an estimated worth of the damage as the actual value was being progressively claimed through insurance as the repair work was completed.
He said there had been no delay in the projected timeline because fixing the damage was able to be done along with other works.
"However, there has been significant staff time involved in, for example, dealing with the police and insurance matters and planning for the repair works."
The additional funding needed to cover the costs was included in a budget increase revealed in July.
The project's previous budget was $22.5 million but would now be $33.7m, with the council contribution to this almost doubling from $11.5m to $22.6m.
The original budget set in 2017 was $17.9m. The opening date has also moved to June next year.
