Christchurch Tenants' Protection Association Spokesperson Lisa Coulter said flatting violence was one of the most difficult tenancy disputes to solve.
She said the Residential Tenancies Act covered disputes between landlords and tenants, but not between flatmates.
The problem was the disputes were not tenancy disputes, even though they were taking place in the context of a tenancy contract, which made people legally attached to each other, Coulter said.
She said the association received at least one complaint every few weeks.
In one case, a tenant had developed a methamphetamine addiction, threatened to kill their flatmates and damaging the property.
"What's really difficult in a flat, is that all the people, often have the right to live there, so it's not as easy to extract yourself from a violent relationship," Coulter said.
She said if flatmates co-sign a lease no one offered to move out when disputes arose, "it can simmer along for a really long time".
Coulter said If students end up in a violent situation they should call the tenant's protection association or speak to the police.
University of Canterbury student Tieta Soewarto said she was racially and violently abused by a flatmate when he objected to the noise her hair dryer was making. She had forgotten to shut her bedroom door and hair dryer noise was too loud for the flatmate.
"It was insane and I remember feeling so scared, because he just yelled at me... he almost slapped me, but I caught his hand."
Soewarto did not want to stay in the flat, nor deal with the police. Her partner had a house, so she moved there to avoid having to see the flatmate again.
"The experience was quite traumatic," she said.
Soewarto said Canterbury University should provide education for students on how to be a "decent flatmate".
"I think the students' association needs to have a seminar on flatting and inform people what behaviour is acceptable, when to call the police, and when to call the [tenancy] tribunal," Soewarto said.
Soewarto has since received counselling and support from the Canterbury University Health Centre.
Another student, who did not wish to be named, said she felt "trapped and powerless" after being locked into a leasing contract with a violent flatmate.
The flatmate was physically violent once and regularly threatened his flatmates, said the student.
"After asking him to keep the noise down at 3am, he threatened to 'snap my spine' in a really abusive tirade," she said.
"He's created an atmosphere that we just have to go along with his lifestyle that directly clashes with ours as students."
She went to the Tenancy Tribunal, but because all the tenants were on the lease the flatmate could not be kicked out.
The young woman said the experience had left her feeling afraid, exhausted and never wanting to go flatting again.
"I understand why there are restrictions in place on kicking out flatmates, but I think there has to be room to kick someone out if they have behaved in a violent or intimidating way," she said.
University Of Canterbury Students' Association President Joshua Proctor has been approached for comment.