Tony Carey employed a contractor to demolish the structure and rebuild it as a single storey replacement.
But instead he says builders Ultra Restore simply removed much of the brick work - as well as a door - and have not been heard from since.
Ultra Restore Preston, based in Lea and whose director is named Billee Hopkinson, has since gone into liquidation on December 30 2021.
Tony, a 33-year-old plaster, contacted the company after seeing its van around the local area.
He handed over £6,200 for work and materials ahead of the project but after pulling down large parts of the extension - leaving a trail of rubble in their wake - no-one from the company has returned.
He made several unsuccessful attempts to contact Ultra Resource without success.
Ultra Restore Preston, whose director is named Billee Hopkinson, has since gone into liquidation on December 30 2021.
Tony, of Blackpool Road, Ashton, said: “They’ve just completely ruined my house, and have basically walked off with my money as well - a lot of my money - and that’s the situation I’m at at the minute, so I just thought it might be good to let people know about this kind of situation.”
After paying more than £6,200, Tony says the builder only did part of the expected work, leaving his house in an unsafe state, before disappearing for over three weeks, and failing to respond to any messages.
Tony said: “I’ve got an existing extension on the back of the house that’s old, so I needed it to come down and I asked him to put a new single story extension on the back of the house instead.
“He took half of the existing extension down but he’s left it in a dangerous state, and it’s an absolute mess.
“I also asked him to dig up my garden to put in a new drainage system and he’s just completely ruined everything, and then he’s taken the back door off as well so my house is now sat vulnerable, plus he smashed a window.
“It’s made us very upset and quite angry, and the house has been left in such a bad way after spending quite a lot of money so obviously it’s affected me mentally and physically, because it’s caused family arguments and financial worries.”
Tony added that from his own research online, he has found two other people who say they have been left in a similar situation.
Lancashire Trading Standards have confirmed that they have received information from Tony, and that they will look at any other relevant complaints referred.
Dawn Robinson from Lancashire County Council Trading Standards Service added: “We cannot comment on individual traders.
“However, rogue cold callers are a huge problem in Lancashire- we received over 900 complaints from defrauded householders in the last 12 months.
“Our best advice is never to deal with cold callers, obtain quotes in advance from three traders and check these include a full name, address and price, take time to think about whether you want to go ahead with the work, and do not pay large sums of money up-front.
“Be wary of doorstep callers offering special rates for pensioners or saying a discounted deal is only available that day- do not let traders rush you into a decision.
“Please have a chat with friends and family before agreeing to work.
“Lancashire County Council runs a Safe Trader Scheme- if you are struggling to find a workman, it is worth looking on wwwsafetrader.org.uk.
“If you are worried that you have dealt with a cold caller, please refer all the details to the Citizens Advice Consumer Helpline on 0808 223 1133.
Billee has strongly denied these claims and you can read his full side of the story here.
Want to see fewer ads? Subscribers to the Lancashire Post get access to the ad-lite version of our website, which features 70% fewer ads and faster load times for a better experience. Find out more