Mrs Johnson's 270sq m home, built in 1995 and which she bought in 2003, showed no signs of being leaky until two years ago, she said.
"My mother died about two years before I fixed the house and left me just over $300,000 and I had some money I had saved. I had to borrow from my son's trust fund and that's how I got the money," she said.
Compensation via courts was too expensive and impossible at the Weathertight Homes Tribunal because the house was older than 10 years.
Ms Thorn is seeking owners of plaster-clad New Zealand buildings to join her action, where she expects damages "well in excess of $100 million" to be sought.
The case is not limited to houses and she also called for owners of office blocks, hospitals and other buildings to register at www.goodcladding.co.nz.
"This claim comes about as a result of the many approaches I have received from the owners of buildings constructed using Harditex, Monotek, Titan board and various different polystyrene claddings," Ms Thorn said, adding that registration would enable her to assess the scale of the claim and gather expert evidence for the case.
About 400 people are understood to have registered their interest in the action, with most claims about $200,000.
A representative of materials company James Hardie in Sydney, which made Harditex, Monotek and Titan board, said the company would not be commenting on the lawsuit.
Ms Thorn refused to disclose who was funding the class action but said they were "international".
Paul Grimshaw of Auckland law firm Grimshaw & Co, which acts for about 6000 leaky-home owners, said that if the action succeeded, people overseas stood to benefit financially.
"Owners will need to look carefully at the terms they are signing up to. Litigation funders often take a percentage of any recovery. So if that is the case here, owners need to look at their net recovery once the funder is paid. In other words, cases like this are often high risk high reward for the funder - a hefty fee if they are successful and nothing if they lose," Mr Grimshaw said.
He predicted a tough battle through the courts, saying the action would have to prove the cladding systems failed.
His firm had taken action against cladding manufacturers, but not along the same lines as Ms Thorn's action, he said.
"What's novel about this case is that the owners are saying that the cladding systems are flawed and that's going to be difficult to establish. The more usual case against cladding manufacturers is where they have had some form of involvement on a site.
"Leaky homes are being built still and reclads are failing - that's the next big thing," he said. "A lot of stuff reclad in 2005 is now failing."
The rot
• Leaky building scandal came to prominence late 1990s/early 2000s
• Hunn Report identified systemic failure
• PwC report estimated $11b-$22b cost of disaster
• Major reforms to building regulations and systems
• But court cases are still going on now
• Experts say leaky buildings are still being built
• $100m class action launched by Adina Thorn
