He never met Magness, who was yesterday jailed for almost four years, and learned of the P lab only when police notified him they were planning a raid on it.
He arrived to find the windows on the shed boarded up and two padlocks on the doors.
Inside, police found chemicals and equipment for making P.
Cameras and security lights were mounted on the outside of the two-bedroom home.
The owner had hoped only the shed was contaminated, but a specialist cleaning company found the home, drainage system, soil and even the septic tank were affected.
The man said his insurance company took a bit of persuading before paying for the loss of the house, and $50,000 of that was spent on the cleanup.
His bank insisted on refinancing the mortgage because there was no longer a house on the property to rent.
Magness was sentenced to three years and nine months in prison when he appeared in the Auckland District Court after earlier pleading guilty to four charges, including manufacturing and supplying methamphetamine.
Crown prosecutor Asishna Prasad told the court that Magness had "cooked" P on the property at least 12 times.
"Usually the victims in this offending are difficult to identify, but in this case we have a real victim put under stress and financial difficulty."
Magness' lawyer, Steve Cullen, said his client had his front door kicked in by gang members who told him they would be storing methamphetamine chemicals in his shed.
Magness shook and wept as Mr Cullen described how his client had become addicted to P himself and was sorry for what he had done.
Judge Mary Beth Sharp said she had no doubt Magness was sorry but his remorse was more about the situation he now found himself in.
Many of the combustible chemicals used in cooking P - including solvents such as methanol and benzene - are fatal if swallowed.
When police find a lab, they notify the local council and the information is recorded on the property's Land Information Memorandum report.
The owner must then arrange toxicity testing and decontamination.
Once the property has been professionally decontaminated, a second toxicity test is done to ensure there are no lingering chemicals to harm occupants. Some clean-ups have cost more than $100,000.
Meth Solutions director Miles Stratford said that on average, one house a day had to be decontaminated.
Forensic consultant Todd Sheppard, of specialist decontamination company Enviro Check Forensics, said his company was "flat out busy".
"I couldn't even tell you the number of calls we're getting," he said from a decontamination site in Rotorua yesterday.
"Fifty per cent of the samples we do are coming back positive, and we've been holding that figure for three months," he said.
"Sometimes the only thing left [uncontaminated] are the outside lights on the walls. It's all over everything."
Most insurance companies do not cover the cost of testing and decontamination, and some refuse to cover rental properties where meth labs have been found, meaning they cannot be re-let.
The Insurance Council did not have statistics on how many houses were affected by meth.
"But anecdotally, meth damage has gone up," said operations manager Terry Jordan.
"Owners can help themselves by putting in meth alarms. They send a report as soon as they detect the chemicals used to make meth. That would be ideal."
Additional reporting: Anna Leask
