Web developer Obi Ljeoma thought he had rented his Cardiff property to four tenants and was unaware it was instead being used to house cannabis plants, Wales Online reported.
While the cause of last week’s blaze is still being investigated, firemen found amateur electrical wiring alongside a large number of cannabis plants.
Ljeoma did not have insurance on the property and has estimated it will cost thousands of pounds to fix the gutted house.
He said by giving the tenants his only keys to the property it had difficult to keep regular checks on the occupants: “The rent kept coming in regularly, so I thought everything was fine. I now realise it was pretty naive of me.”
“I’d like to warn other landlords to keep a close eye on their properties, because you never know what could happen.”
Ljeoma, who lives in Berkshire, bought the property ten years ago when his son was studying in Wales and consequently decided to rent it out.
When he signed the latest lease the tenant had told him four people would be living in the property. There had been no signs of trouble for eighteen months.
The landlord plans to refurbish the house and rent it as flats. He said: “I’m not put off from renting properties, but I will be a lot more cautious in future.”