Both detailed the way in which Ashley operated would evolve depending on staffing, funding, public scrutiny and the use of isolation on detainees.

"The easiest way to explain it is that it's f***ed me in the head for a very long time. It made me into a lot of things that I wasn't when I first went in there," one former detainee, who experienced Ashley over a decade ago, said.

He welcomed news that it would close within three years, and urged the government to ensure that their two new centres - one in the North, one in the South - were staffed by people with training in childhood trauma.

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The other, who entered the youth justice system aged 11, said it was a prison-like setting to start with, but then it would change based on the management at the time. He was sent to Ashley more than 20 times.

"Going back a few years ago, I would've said, 'yep, I'm going to Risdon after this'. But then something clicked in my head. I didn't want to do this. And once I had that thought, I started reaching out in Ashley," he said.

"And once I started reaching out, Ashley was the place that helped me to change. The workers liked the ones who would put the effort in.

"I saw a few different lives of Ashley, some good and some bad. If they kept me on the street, someone would've been seriously hurt."

Their two contrasting experiences over different iterations of Ashley reflected just how challenging a custodial-style youth justice system could be.

Both have made allegations of sexual abuse in Ashley.

Premier Peter Gutwein announced on Thursday plans to close Ashley and construct two new facilities to house young offenders in a more therapeutic setting, with improved links to service providers and families.

The decision comes after he met with Ashley clinical practice consultant Alysha for over two hours on Wednesday, who detailed her fears for the safety of children in the centre.

There have also been a series of allegations regarding the centre - including historic sexual abuse, with a former detainee taking action in the Supreme Court - and repeated concerns raised by the Custodial Inspector. The Commission of Inquiry into child abuse allegations will also focus on the centre.

Alysha - who claimed she was sexually harassed by a colleague shortly after she started working at the centre - said her first reaction to the announcement was "absolute overwhelming relief".

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"I think that I might have the first night of solid sleep that I've had in two years," she said.

"Nothing takes away the harm that has been done, but I think that closing the centre as a matter or urgency is the least that we can do for past and present."

Alysha said Mr Gutwein listened intently to her experiences of Ashley, with her describing the "first 10 minutes" of their chat about the handling of her sexual harassment complaint, and the remainder of the meeting discussing her child safety concerns.

She said having the new therapeutic-centred centres in the North and South based in cities, rather than separate like Ashley, would go a long way to aiding in reintegration for young people.

Mr Gutwein said his conversation with Alysha was "another piece in the puzzle" in coming to the decision.

Closure of Ashley was one of four options put forward following the Noetic Report into youth justice in 2016, but the government chose another option of retaining it, but with upgrades.

Earlier this year, a further $7.3 million in upgrades started, which will run their course.

A decision on the future of the Ashley site will be made in the coming years. Mr Gutwein would not be drawn on whether it could house an adult system, rather than building a new one near Westbury.

Lawyer Angela Sdrinis, who collated 120 cases for a class action against the government regarding Ashley, said the government was "playing catch-up" and was in "damage control" by decision to close the centre.

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"It knows what is coming as the Commission of Inquiry commences its work," she said.

"The government must ensure the safety of children whilst any new facility is being built and must invest further in diversionary programmes and proper rehabilitation for vulnerable young people who are at risk and engaging with the juvenile justice system."

Prisoners Legal Service Tasmania chair Greg Barns has long been calling for Ashley to be shut down, claiming it has an almost 100 per cent graduation rate to the adult system at Risdon.

He welcomed the decision, and called on the government to work with youth justice experts, courts and the PLS to develop more therapeutic approaches to youth justice.

In a statement, the government confirmed it would consult with the Custodial Inspector and the Commissioner for Children and Young People in transitioning to the two new centres.

While the decision to close Ashley was broadly welcomed across the political divide, there were still some concerns looking to the future.

Tasmanian Aboriginal Centre campaign manager Nala Mansell was worried about the announcement to build two new youth justice centres, pointing to the defunding of past Aboriginal-led diversionary programs.

"Children need to be able to access programs and services aimed at rehabilitation outside of prison wall settings," she said.

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"It is ridiculous to expect better outcomes for young people while continuing the lock up approach."

Former Western Tiers MLC Greg Hall described the closure as a "knee-jerk political decision".

"I think it's an ill-considered attack on the people that work and have worked there in a very challenging environment," he said.

"Our justice system currently ensures that a strong diversionary approach is taken to ensure as few young people end up in secure facility anyway."

Mr Gutwein said his decision came down to the culmination of years of concerning issues emanating from Ashley.

"The events of this week have firmed in my mind that despite the best intentions of management and staff, the centre will continue be stigmatised and constrained in terms of the outcomes it can achieve for young people," he said.

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