Stuart Dye, 77, lost £3,000 in a “sloppy” job when he tried to have the roof of his four-bed detached house repaired.
After paying in advance, he went to inspect the work and found what he described as a “complete mess”.
The pensioner later discovered that tiles had been taken from his neighbour’s garage to lay on himself.
And he said he was sickened seeing footage of those responsible filming themselves “ruining” another job while boasting about ripping off an elderly victim.
Those responsible Matty Rossiter, 18, James Rossiter, 25, and Dean Smith, 21, were jailed last week for what a judge described as an “industrial-scale” rogue operation.
The trio videotaped themselves bragging about ousting 82-year-old John Bray, whom they described as “very old.”
They said on camera “we find guys like this every day” by “knocking from door to door”.
In total, between October 2020 and March 2021, they made £45,000 from crimes committed at 18 properties in Wiltshire, Gloucestershire and Bristol.
One of the victims, Mr Dye, said he came forward after watching the video recorded to build the case against them.
He added: “A few months into the job I was watching the news and I saw these three on video making fun of the poor guy.
“I called the police on the helpline and just said I knew them. They laughed at this elderly gentleman and it just sickened me. To see them stoop so low and take advantage of someone so vulnerable.
“It’s disgusting – I felt so sorry for him.”
Mr Dye said he is now awaiting the legal process to determine how much of his money, if any, he will get back.
And he said he was “baffled” by the trio and felt “ashamed” to have been ripped off by them.
He added: “I contacted other local builders and messaged them but no one answered their phone. Finally I got this Yates Roofing from the internet. They had a nice website so I called and they came two days later and said they would do the job.
“I paid them upfront, which was a stupid thing to do, and left them to fend for themselves.
“I went out and what a mess they had made of the garage. Instead of taking the tiles off they just put a layer of cement over it. They stole a tile from my neighbors garage. They broke it just off their roof and onto mine.
“It was so brutal. As soon as I saw the work I realized I had made a big mistake. I told them ‘your work is horrible’ and I want my money back. They just said ‘great chance of that’.
“I told them I’m moving forward with this and I wouldn’t allow them to do any more work on my house.”
Mr Dye said his builders came in a new van and “looked professional and seemed to know what they were doing”.
He then went to their registered property in Yate and discovered that it was fictitious and that they had advertised under a number of different names.
He added: “Their behavior was friendly, not aggressive and not heavy-handed. I felt stupid and ashamed that I had fallen for an obvious con artist.
“I’m very thankful that they were being chased. These people want to stop and the only way is proper jail time and deprivation of their belongings. I wouldn’t classify myself as vulnerable, but they prey on those kinds of people. I just got caught. guard.
“I’m even more suspicious now and on my guard all the time. It makes you realize how easy it is to get caught.”
On the phone footage, one of the three defendants says, “As you can see we’re doing some roofing here. We’re doing some bodging.”
The camera then pans to look at the poorly repaired roof, before the cameraman adds, “As you can see here, we don’t have to pay thousands for advertising.
“It’s door-to-door knocking, which I’ve done all my life, and we find guys like this every day. The door-to-door knocking. It’s the way forward.”
The work was later labeled “bottomless” by a chartered surveyor named by Wiltshire Trading Standards.
It was “carried out without associated skill or competence” and “probably without the use of suitable hand tools”.
Matty and James Rossiter, both of Minety, in Wiltshire, admitted fraud through false statements and participation in a fraudulent enterprise.
Matty Rossiter was jailed for two years and three months, while James Rossiter was jailed for three years and four months.
Smith, of Aldermaston, Berkshire, was sentenced to three years after pleading guilty to participating in a fraudulent enterprise.
Mr Bray’s son Steve had previously told the BBC that the group was ‘despicable’ and he believed his mother’s death was partly due to the fraud.
Judge Jason Taylor of Swindon Crown Court branded the trio as rogue builders on an industrial scale and reprimanded them for their ‘arrogance’ after making fun of their victim.