John Thompson, trading as Thompson Roofing and Guttering, told the couple that the structure of their roof was to blame for the labourer's fall. He claimed the battens and timbers were rotten and spaced too far apart and charged them £7,200 to carry out repair work.
Neighbours alerted Buckinghamshire and Surrey Trading Standards, whose officers notified the Health and Safety Executive (HSE) and this led to a joint prosecution.
Last year, Thompson admitted breaching reg 6(3) of the Work at Height Regulations and pleaded guilty to fraud and engaging in a misleading commercial practice. He was jailed for two and a half years earlier this month.
Guildford Crown Court was told that Thompson cold-called the couple, who are in poor health, with one suffering from dementia, at their home near Leatherhead in March 2017 after doing some work on a property nearby and offered to repair a section of guttering for £40, which was agreed.
He then told them he needed to survey the roof but failed to put up scaffolding. One of his labourers fell into the loft below, causing significant damage.
When Thompson billed the couple for the work, he included scaffolding in the cost despite failing to provide it.
The HSE's investigation found that several people were at risk from the work being carried out because no measures were in place to prevent labourers from falling.
An independent expert who examined the roof on behalf of trading standards found the hole was solely Thompson's fault and not down to any structural defects. The expert was also critical of the standard of repair work carried out.
Denise Turner-Stewart, Surrey County Council's cabinet member for community safety, fire and resilience, said: "Rogue traders callously prey on the most vulnerable in our society and our trading standards officers work hard to bring them to justice and keep our communities safe. I would like to thank the neighbours of this couple for their vigilance and for alerting us to their concerns."
