safety executive appalled at renovation work .
The £38,000 extension was supposed to add two more bedrooms to the property - but the upper floor of the house ended up caving in when the roof was removed, completely destroying the floor below.
Their son also suffered a broken leg, as he was inside the house when the incident happened.
A subcontractor was seriously injured too, and fire crews were called out when the home collapsed.
© BBC James Hobby told his story on BBC: Rip-Off Britain
The cause of the accident was down to the builder failing to prop the gable, party wall and chimney.
Mr Hobby and his wife, who share their home with their two sons, were away on holiday while the work was taking place.
Speaking on BBC's Rip Off Britain TV show , Mr Hobby said: “We were really in deep shock and couldn't really comprehend how that could possibly have happened.
"The damage was so extensive and the injuries were shocking. I was completely shocked by it."
Mr Hobby told the BBC that his building insurance wouldn’t cover the damage, due to a clause that states it won’t pay out for poor workmanship.
© BBC The family have since had to fork out £250,000 to fix the damage