The mummified body found under rubbish at a house on Sydney's lower North Shore has been identified by police.

Shane Snellman's remains were rolled up in a carpet and found by cleaners at a deceased estate in Greenwich last Tuesday.

The property owner, Bruce Roberts, died from a suspected heart attack last July and police believe he may have been responsible for the death of Mr Snellman.

It is understood Mr Snellman was estranged from his family and was known to police for petty crime.

Senior police sources told the ABC Mr Snellman's body had been hidden away at the house for at least a decade.

It was found in a room at the property and a post mortem revealed Mr Snellman sustained several injuries before his death.

Police are still trying to work out the relationship between the two men.

When Mr Roberts died, he donated the majority of his will to a number of charities and a cousin who lives in rural New South Wales.

Neighbours have described him as a hoarder and a recluse who had little contact with people when he lived in Greenwich.

Local supermarket owner Paula Truong knew Mr Roberts for 18 years.

"Bruce used to come down to the shop almost everyday," he said.

"He would pick up a newspaper and some groceries, but he definitely isolated himself.

"He didn't really talk to anyone, but he was always friendly to me and I thought he was a good guy.

"It really surprises me that a body was found in his house because he lived alone — I am very shocked to hear that."

Bob and Gayle Meagher, who lived next door for 20 years, described Mr Roberts as a loner.

"It's creepy and sad. It's just awful that it's next door, very unpleasant," Mrs Meagher said.

Mr Roberts' parents had owned the property and he had lived there for 40 or 50 years, she said.

"He was paranoid about security around the home and had barbed wire," she said.