Craig Franklin, 48, pleaded guilty in Warrnambool County Court on Wednesday to charges, including arson and driving offences.

He was sentenced on Friday to three years and three months' jail with a non-parole period of 21 months.

Franklin has already served 591 days in custody on remand and will therefore be eligible for release on parole in about August.

Judge Michael O'Connell said Franklin and the victim purchased a property together in Warrnambool in 2018.

He said the man suffered depression and alcohol abuse, which led to Franklin moving into a caravan at Nullawarre in October 2019.

The judge said on October 25, Franklin sent text messages to the victim stating he wanted to make her suffer.

The victim did not respond but requested police to conduct a welfare check.

Officers attended the man's caravan and Franklin was admitted to a mental health unit under the Mental Health Act.

Judge O'Connell said Franklin was suffering psycho-social stress, alcohol-use disorder and intrusive thoughts of harming himself and others.

The court heard Franklin left the South West Healthcare mental health unit on October 30, 2019, and walked to the family home in Wares Road, arriving at 3.24pm.

Less than five minutes later a neighbour noticed flames coming from the window of the house.

Franklin fled on a motorbike at speeds exceeding 150km/h on the Princes Highway and over 100km/h through roadworks on the Great Ocean Road, and did not stop on police request.

He then returned to the mental health unit.

Judge O'Connell said the man told police he didn't know why he set fire to the house and that he "just snapped".

"You went back to the ward and owed up to what you had done," he said.

The judge said the victim suffered emotional and financial impacts following the offending and was forced to live in a motel room for some time after the house was gutted by fire.

He said Franklin had a disadvantaged upbringing and started drinking alcohol at the age of 10, using cannabis in his late teens and amphetamines in his 20s.

Earlier this week, defence barrister Rohan Lawrence said Franklin was plagued by suicidal thoughts and struggling emotionally at the time of the offending.

He said the fire was not premeditated and that Franklin was aware there was no one inside the house.

If you or someone you know is impacted by sexual assault, domestic or family violence, call 1800RESPECT on 1800 737 732 or visit 1800RESPECT.org.au. In an emergency, call 000.

Emma House is a Warrnambool-based not-for-profit service and can be contacted through 1800 EMMADV (1800 366238) or visit emmahouse.org.au/

Safe Steps for women after hours service is available through 188 015 188.

Brophy Family and Youth Services can be contacted on 1300 BROPHY or 03 5561 8888.

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