Dean Mason, who owned the Birch St building, and Dougal Weily, who owned the Japanese Auto Wreckers Ltd business located there, hoped the reward would flush out the person responsible for the suspicious fire on March 2 last year.
The $10,000 reward would be paid when an offender was identified and successfully prosecuted, Mr Mason said.
Mr Mason began rebuilding on the Birch St site, near the Dunedin harbour basin, earlier this year.
Mr Weily's business reopened in Kaikorai Valley in July last year.
However, both told the Otago Daily Times they were frustrated the offender had not been caught, given the toll the blaze had taken on their lives.
Mr Mason said a prosecution would provide some "personal satisfaction" after a year from hell, battling the Dunedin City Council to obtain resource consent for a replacement building at the site.
He hoped the reward would encourage someone to come forward.
"Loose lips will sink ships."
Mr Weily said both men had been left out of pocket as a result of the fire, and he estimated his losses at $250,000.
He was insured for losses up to $100,000 but had stock inside - including vehicle parts delivered the day before the fire - worth more.
He had also lost revenue while the business was closed.
"It's been very hard. We have had to still pay all our suppliers.
"It was pretty crippling, really.
"We think someone would have seen something or know someone.
"I'm sure there's someone that $10,000 would be quite handy for."
Senior Sergeant Steve Aitken, of Dunedin, said, when contacted yesterday, the police file remained open.
Any leads would be followed up, he said.
The fire that destroyed the Birch St building and Japanese Auto Wreckers business was one of two suspicious fires - believed to be linked - started on the same morning.
The second fire, at Independent Tyre Specialists in King Edward St, began within about an hour of the Birch St fire.
Both were started in piles of tyres outside the businesses, Detective Sergeant John Hedges, of Dunedin, said at the time.
Yesterday, Mr Mason said construction of a new 1150sq m industrial building - with a 210sq m administration block - was under way, following prolonged negotiations with council staff.
The development - expected to cost about $1 million - was scheduled to be completed by the middle of this year, and a search was under way for a new tenant, likely to be an engineering or warehouse storage firm, he said.
• Barbeque Bill Catering managing director Tony Cummings had no new leads yesterday, after offering a $1000 reward for information leading to a conviction over the apparent arson of one of his company's vans on Monday.
