The businessman spoke to The Advertiser before climbing into an excavator to tear down a wall at the fire-ravaged old laundries, at the back of Kennington Primary School.

Mr Arthur carefully knocked the bricks outwards to give forensic investigators and the Melbourne-based Arson Squad safe access to the crime scene.

He had attended the blaze shortly after it broke out on Wednesday and has had little rest since then.

The exhausted businessman was told by insurers yesterday the damage was estimated to be valued at between $400,000 and $500,000.

Mr Arthur, who owns BDA Constructions - which is carrying out building work at the site - said he was also upset that a part of history had been lost.

"There's a lot of historical significance in that centre part."

He had planned to renovate part of the old laundries.

However, the blaze destroyed two-thirds of the building.

The remaining third may have to be knocked down because it is feared to be structurally unsafe.

Mr Arthur said if it was possible to preserve the remaining part of the building, he would.

"They have maybe saved that centre section," he said of the firefighters' efforts. "We want to keep it."

Mr Arthur's workers live nearby in the complex.

He said he was relieved no one was injured in the blaze.

"It's amazing.

"The fire brigade did a great job."

Mr Arthur said he was also grateful to the Country Fire Authority crews for containing the fire and preventing it spreading to the main orphanage buildings.

"It looks like there's no damage to the school and our main buildings.

"They're safe - which is a relief to us."

The fire also left the old orphanage site without power.

Mr Arthur said he was trying to remain positive.

"We've just got to get on with things."