WA Premier Mark McGowan says the estimated damage bill following last week's riot at Banksia Hill Juvenile Detention Centre has come to about $30 million.
The riot, which broke out last Tuesday night, lasted more than 12 hours and involved 47 detainees.
The inmates began moving within the grounds and onto the roof of the centre, lighting fires and damaging infrastructure.
Mr McGowan said the damage will take some time to fix.
"The initial estimate's about $30 million worth of damage because the detainees set the place on fire then they stopped fire trucks coming in, so the fires got worse, and then all the water damage from putting out the fires," he said.
"There's a lot of disruption there and there'll be people being transferred to what's called unit 18 at Casuarina [Prison].
"I expect that a lot of the programs won't be fully operational and a lot of the activities won't be fully operational. That's unavoidable."
Mr McGowan said rioters particularly targeted control rooms which house electronics and cameras, making it more expensive and difficult to fix.
He has repeatedly condemned their behaviour, describing the riots as "appalling" and has urged people not to defend it.
Four riots in a year
WA Opposition Leader Shane Love has condemned the government for not doing enough to prevent such incidents.
"That's the fourth riot we've had this year at Banksia Hill and the minister and premier have not acted to ensure that the community and the staff that work in that facility are safe," he said.
"As a result, we've seen $30 million of taxpayers funds go up in smoke at Banksia Hill."
"The premier needs to act."
Mr Love called for the replacement of Corrective Services Minister Bill Johnston with someone who could keep the community and staff at Banksia Hill safe.
Mr Love accused the government of downplaying the issue and lacking transparency, saying there isn't a clear plan to address the range of issues at the controversial centre.
"We know that there was a 90-minute summit where all these positions were supposed to be discussed, and resolutions reached, but no minutes were kept," he said.
"We asked for the notes that the premier had taken to be tabled in parliament, and he wouldn't do so."
New legislation being introduced
Tomorrow, the state government is set introduce a bill in parliament to amend the Young Offenders Act 1994, which will ensure juvenile detainees are moved to an adult prison as soon as they turn 18.
Premier Mark McGowan said historic legislation meant a detainee could remain in a juvenile facility past 18 if their sentence began while still a juvenile.
"There is currently one detainee who is 23, now I don't want a 23-year-old mixing with a 14-year-old," he said.
"What we're going to do is just make sure that adults go into adult custodial facilities, and we protect those who are juveniles.
"Six of the participants in the riot the other night were over the age of 18, now if they're going to, as adults, participate in a riot then they're going to go into adult prison."
Mr McGowan said it would bring WA into line with legislation elsewhere around the country.
Prisoners on remand create 'tinderbox'
When asked for further information on the riot at a press conference on Sunday, the Premier Mark McGowan said prisoners on remand generally had more issues than convicted prisoners.
"Even though you're not convicted of an offence, you often will have a range of drug or alcohol or other issues that are still in your system when you first arrive there, that once you're there for a while, come out of your system," he said.
"If you put those remand prisoners together, you may well be creating a tinderbox where they're not actually mixing with others."
When asked questions about the possibility of a second centre for juveniles on remand at the same press conference, the premier said it would not be viable given the extra staff needed to operate the facility.
The premier questioned the previous government's decision to shut down Rangeview Remand Centre for juveniles in 2012.
"They need to answer why they did that," he said.
Corrective Services Minister Bill Johnston said 30 of the 47 detainees involved in the riot were remand prisoners and "had been given to the care of Banksia Hill because they'd been violent in their own communities".
The government also said it would take five or 10 years to build a new facility.
