Charles O'Brien, 38, was sentenced to more than two years after he pretended he was a qualified tradesman, before scamming four OAPs out of thousands of pounds.
The Irish dad-of-six wept in the dock at Kilmarnock Sheriff Court as his crimes against the couples were revealed.
As he was sent down, O'Brien shouted "There's no justice in Scotland".
The court heard O'Brien, who is originally from Ireland but now lives in Irvine, North Ayrshire, targeted a 76-year-old man and his 74-year-old wife on February 16 this year.
O'Brien visited the couple's Whin Hill Road home in Ayr, South Ayrshire, and told the trusting pair that their house needed a new roof and that an exterior wall needed to be rough cast.
The rogue tradesman then told the couple he was a qualified roofer and roughcaster and would need £15,780 cash upfront to buy materials.
The unsuspecting couple handed the cash over believing that the work would be carried out.
However, the court heard that not only was O'Brien not qualified to carry out the work, but the roof and wall did not even need repaired and O'Brien never purchased the materials.
The court was told that O'Brien even had the gall to demand a further £4,800 from the couple, which they did not pay him.
Just weeks after the first scam, O'Brien found another trusting elderly couple in Main Street, Drybridge, North Ayrshire, and tried to dupe them out of £18,000 to replace guttering and felting on dormer windows.
The scammer told the 79-year-old man and 80-year-old woman he would need an advance of £2,000 for materials then went back and demanded a further £5,000 from them before they refused to pay him the total lump sum.
O'Brien's solicitor pleaded with Sheriff Alistair Watson to spare his client jail for the sake of his family and six children - one of whom, he said, had "learning and physical difficulties".
The defence brief said: "His position remains that he is gravely sorry and remorseful for his conduct.
"He feels sorry for the impact that it has had on his victims and his own family.
"He is someone who, through his community has developed a number of skills in labouring and construction and monoblocking.
"It's a skewed view of the reality of his qualifications."
But Sheriff Watson told O'Brien, who appeared in court for his first scam before committing the second, he could see through his tears.
He said: "Given the nature of the offences and the sums of money concerned, the only appropriate sentence is a custodial sentence.
"This was a course of criminal conduct directed towards elderly people.
"You selected victims who were elderly and who were fooled by you and you stole their life savings.
"Crying does not impress me at all.
"You are feeling sorry for yourself when what you should have been doing is thinking about those unfortunate people who have lost money.
"The effect on your victims is likely to have been highly significant.
"You persisted in this criminal behaviour and you appeared in court for the first matter and went on to commit the next crime in a matter of days."
O'Brien was sentenced to 28 months in prison.
As he was led away in handcuffs he shouted, "There's no justice in Scotland."
Sergeant Jamie Dunlop from Police Scotland said: "Bogus callers and rogue tradesmen are professional liars who regularly prey on the elderly and they can be extremely convincing when they come to the door offering their services.
"We would advise that if someone approaches you claiming to be a tradesman - ask for their identification, and if you are still unsure, call the company to verify that they work for them."