Geoff Rollason and his wife Angela landed in trouble after deciding to transform the garage into a utility room at their home in Parkfield Road, Stourbridge.
They gave the job to Scott Lewis, who was listed as an alleged member of the Federation of Master Builders, to do the work which he estimated would take ten weeks to complete and cost £35,300.
Three years later it has still not been finished and the 55-year-old bodger has received a five-month prison sentence suspended for two years after admitting two charges of unfair trading through lack of due diligence between November 1 2016 and March 31 2017.
His blunders included attempting gas work he was not trained to do without warning his employers.
Lewis also failed to connect a storm water drain to the sewer and put down a patio which had to be dug up and relaid.
"The standard of the work throughout was poor and Mr and Mrs Rollason were entitled to expect something far better," said Mr Richard Franck, prosecuting on behalf of Dudley Council.
Lewis walked off the job without it being completed after receiving £32,000 towards the total cost of the project.
Some of his work was so bad Mr and Mrs Rollason have had to spend a further £11,000 correcting his faults with £4,000 more needed to finish the saga.
Ms Sarah Allen, defending, maintained: "He failed to recognise issues as they arose, such as the drainage system. This was through ignorance rather than wholesale negligence."
She said his work started to dry up following complaints about its standard being made public and was forced to declare himself bankrupt, ruling out compensation for the Rollasons.
Judge Simon Ward told Lewis, from High Heath, Whitchurch, who also received a tagged night time curfew until March 29: "The Rollasons were really unfortunate to get you. This was a nightmare for them because you were not sufficiently competent to mend your own mistakes.
"Your behaviour was not fraudulent but your inability to recognise you could not carry out work to a decent standard has cost this couple a considerable amount of money."
Mr Rollason said after the case: "He is just an incompetent conman."
His wife added: "We knew we were not going to get anything back but we didn't want it to happen to anybody else. We are pleased he got a tag for Christmas and New Year."