Mandatory safety locks on windows will not protect children from falling out of the windows of older style units, a leading engineer says.
Apartments built between 1950 and 1970 do not have sufficient frameworks to support the weight of a child leaning against it, even if they are locked, strata engineer Chris Mo'ane said.
Mr Mo'ane said the older windows had the same level of support as a flyscreen and could ''fall out'' even if a safety lock was attached.
Of the 70,000 strata schemes in NSW, more than half are for buildings built between 1950 and 1970, figures show.
Mr Mo'ane will submit his concerns to the government during a six-week community consultation period, which started this week.
The proposed safety measure will require every apartment in NSW above ground level to fit a safety device that would prevent the window opening more than 12.5 centimetres, or the size of a child's head. The legislation will go to Parliament in July, where it is expected to be passed.
Legislation has been passed that will make window safety devices compulsory in new residential buildings from May 1. But the types of locks that will be mandated for units remain open to suggestion.
"We are seeking feedback from the community and industry on their suggestions for which locks might work best in common property areas,'' Minister for Fair Trading Anthony Roberts said. "A lock that can save a child's life costs anywhere between $15 to $40.''
The legislation is also unlikely to be regulated. ''The government is confident that due to the amount of stakeholders involved in the installation process, enforcement won't be necessary,'' a spokesman for the minister said.
"We want people living in apartments to have this conversation with their neighbours and fellow tenants,'' Mr Roberts said.
The grandmother of a toddler who plunged three storeys out of a window in Warwick Farm in 2011 said the proposed law was overdue.
''I think those new laws are the best thing that could happen and I cannot understand why it has taken the government so long,'' Margaret Ranapia said.
''You've gotta have eyes on the back of your head and on top of your head when you're a parent … people that have almost lost their child like we did can sleep at night now.''
The Owners Corporation Network, which overlooks 70,000 strata schemes in NSW, said it would encourage owners to implement the safety devices.