Residents of the Jettys by the Lake seniors "lifestyle village" at Windang, south of Sydney, have been told they need to raise their homes to three metres above sea level within five years - a cost which many would have no way to meet.
And the 3m requirement - newly introduced by Wollongong City Council as a condition of alterations to Jettys' development consent - would mean many older residents couldn't get up all those stairs to their home.
The council says these heights are necessary to protect against predicted flood depth after sea level rises due to climate change.
Long-time resident Lee Johnson said it made no sense for them to raise their homes to 3m, when none of the roads or other homes around were that far above sea level.
If the water rose that far the area would have to be abandoned.
"The whole of Windang and Warilla would be under," she said.
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She said many residents were concerned for their families if they passed away.
"What people are worried about at the moment is we can't sell our house because of these conditions," she said.
"If we die, our families won't be able to sell the house. That's our number one concern."
David Hoffman, director of Jettys owner Hampshire Villages, said the new rule came about as Jettys sought to convert 190 unused short-term holiday sites into 86 long-term residential sites.
"We agree that the council requirement to raise floor levels of homes to a height in excess of 3m appears to be absolute overkill and seems predicated on a view that sea level rise will flood the entire Windang peninsula by 2050," he said.
"We have not imposed a requirement on residents to incur any costs in relation to council conditions. We are currently assessing the potential individual impacts on each site, so that we can determine the best way forward."
He said Jettys had "had little choice" but to agree to the condition in a Land and Environment Court conciliation conference.
"Lake Illawarra Park Pty Limited felt it had little choice but to accept the conditions, as it became clear that the court proceedings may jeopardise the rights of existing permanent residents to remain."
Resident Margaret Jarrett said she bought her "little place" on the understanding it would be where it is. With bad knees, walking up 3m of stairs would be out of the question.
"You tell me how elderly people are going to get up there," she said.
"How are we going to get up those stairs?"
She said Jettys had rarely flooded, and in the major flood of 2016 the water only made it to her second step.
Asked why the homes had to be raised to 3m, a spokeswoman for Wollongong City Council said this was a flood planning control which was now applicable to the Lake Illawarra Floodplain.
"The predicted flood level for 2050, which the minimum habitable floor requirement is based upon, accounts for sea level rises predicted to occur due to climate change," she said.
"This flood level was determined by Council's adopted Lake Illawarra Floodplain Risk Management Study and Plan.
"The condition was placed on the development consent to address the above points."
The council has also resolved to write to the state government. This was "to advise that requirements that allow residential land lease communities to operate are changing in some instances due to revised flood modelling and coastal erosion from climate change and fire safety regulations" and to see what assistance exists.