Emergency services were called to a house in Bukkai Road at about 5.20pm and took about an hour to extinguish the fire.

Lake Macquarie Fire Control Centre's acting team manager Superintendent Paul Jones said the house was well alight when emergency services arrived.

"Both Fire and Rescue and local RFS units responded to the fire. When they arrived they conducted an initial search of the house and discovered the resident [who was then removed]," Superintendent Jones said.

The structural integrity of the building was compromised, so firefighters switched from an offensive firefighting strategy to a defensive one and fought the fire from outside, Superintendent Jones said.

Lake Macquarie detectives, forensic officers and investigative personnel from Fire and Rescue NSW are working together to determine the cause of the blaze.

A report on the death of the 81-year-old man, who was the only resident of the property, will be prepared for the coroner.