Love them or hate them, in a crowded city where living space is in short supply and barely affordable, subdivided flats are here to stay.
Recent tragedies have again highlighted the dangers of these cramped dwellings, with 14 residents killed by fires in buildings in Ma Tau Wai and Mong Kok, at least partly as a result of residential conditions.
Each time something like this happens the government responds by promising to scale back subdivided flats, but experts say the problem is hard to solve, because of economic obstacles and political risks.
'It has already become impractical to outlaw [subdivided flats] given the difficulty of quantifying them and the number of people affected,' Development Secretary Carrie Lam Cheng Yuet-ngor told lawmakers last month, after a fire spread through the market stalls in Fa Yuen Street, Mong Kok, killing nine people living in nearby sub-units.
Buildings Department inspections of 600 flats in 105 buildings since last April discovered 2,300 sub-units - a subdivision of each flat into four units, on average.
'There could be tens of thousands [of subdivided flats] all over Hong Kong,' Lam said.
These flats, ranging from less than 100 sq ft to no more than 300 sq ft, give their tenants a higher degree of privacy than cubicles and cage homes because they include bathrooms and cooking space.
But in order to maximise the return on their floor space, most owners of subdivided properties give little consideration to complying with fire regulations. In many cases, drainage pipes and water seepage weaken the building's structure, while the use of wooden partitioning and blocking of rear staircases also increases fire risks.
'In some cases, owners do not provide a separate entrance for the sub-units,' Lam said. 'They are hidden behind the door of the original flat. Residents have to go through tiny, narrow corridors to get out. The only hint there are multiple residences is the attachment of a few letter boxes to one flat.'
She says enforcement of the law against illegal subdivisions has been difficult as officers can only act on public complaints and must have police officers with them when breaking into suspicious flats.
In face of mounting public pressure for more proactive enforcement of the law, last April the Buildings Department launched a special operation under which 150 target buildings will be identified for inspection every year. The annual inspection is expected to cover about 1,300 subdivided units.
An inspection last July uncovered an eight-storey building in To Kwa Wan which had 51 units carved out of 12 flats. Most units blocked fire-escape stairwells. By the end of November, 64 eviction orders had been issued by the department but to date only 15 of these have been complied with.
The Development Bureau also proposed widening the law to require owners to hire professionals to carry out work relating to subdivisions, including alterations to partition walls and fire-escape routes.
The amendment, expected to be passed by lawmakers early this year, will also make break-in inspections easier by providing Buildings Department officers with the means to obtain a court warrant.
But analysts say confining the issue of subdivided flats only to safety concerns overlooks its wider implications, which involve social and political concerns.
Ho Hei-wah, director of the Society for Community Organisation, sees subdivided flats soon replacing cubicles (partitioned rooms without bathrooms and kitchens) and cage homes because they are more profitable and easier to manage. According to Ho, agencies recommend that buyers looking for investment opportunities should subdivide a flat.
Once owners agree, the agents commission the renovations, rent flats out and collect rents.
'This is really attractive to those hoping to reap quick profits,' he said.
Some agency websites highlight subdivided flats as a profitable investment for buyers. One offers 'high-rental income' for buyers of a Sham Shui Po flat that has been divided into five units.
'Partitioned rooms and cage homes are diminishing in renewal projects,' Ho said. 'Owners are looking for a more profitable business. Instead of separating a flat into 10 or more rooms, they opt for fewer units with higher rental income and easier management.'
Tam Kwok-kiu, vice-chairman of Sham Shui Po district council, sees the phenomenon from a different perspective.
'Those who lived in cage homes in the 1980s were mostly single men working as labourers,' he said. 'They have since gone to the mainland to get married and returned with wives. So they are looking for cheap flats with a little more privacy.'
With more mainlanders visiting Hong Kong, some divided flats - dubbed coffin rooms - are available for rental periods ranging from hours to months. They can be as small as the size of a bed and often unsanitary.
But Tam said he was surprised how popular they had become
'Rents are as competitive as flats in Mei Foo Sun Chuen [an area in Sham Sui Po famed for its high rental yields],' he said.
The Sham Shui Po district council, which has been overwhelmed by complaints of water seepage and other possible threats posed by sub-units, commissioned a study early this year to look into living conditions in sub-units.
The study, conducted by the University of Hong Kong, interviewed 100 households in sub-units in Sham Shui Po and found more than 60 per cent of residents lived in flats of less than 160 sq ft. They worried about the poor hygiene and fire dangers in their living environment.
Most were permanent residents and some had tertiary education. Two-thirds were Hong Kong residents, of whom 66 per cent were aged 30 to 49. Close to a third were aged 80 or over. In terms of education, up to 37 per cent received high school training, including five per cent who graduated from universities and other tertiary institutes. Half of them said they had been unable to obtain a public flat.
The rising number of young adults looking for an affordable space of higher quality has prompted owners and agencies to renovate these tiny flats to get higher rents.
Some have been given a Japanese touch, with wooden tiling on the floors and a semi-transparent screen dividing the unit into a bedroom and living room.
Rents for these 'Japanese houses', with an 'open kitchen' with sink and range hood, can reach HK$5,000. This compares with about HK$2,000 for unrenovated units.
'The huge demand from graduates and young couples has further driven up rents,' Ho said. 'Meagre pay rises and lack of promotions have forced them into these tiny units as they are not qualified to apply for public flats.'
About 60,000 single applicants are waiting for public flats, but the government only allocates a maximum of 2,000 each year to single people.
'It will take them more than 20 years to obtain a public flat,' said Ho.
One applicant applied for a flat when he was 40 years old, and was finally given one 19 years later, when he was 59.
Ho, one of the government advisers to review the long-term housing policy in 1996, wonders why it takes this government decades to provide flats for single people when the colonial administration was able to release 43,000 in four years. He said the situation would only get worse as more educated people had their quality of life lowered because of a widening income gap between them and the rich.
The increase in the sub-division of industrial buildings was a warning to the government about its ineffective housing policy.
Professor Rebecca Chiu Lai-har, a specialist in urban planning at the University of Hong Kong, said the government should consider cutting the waiting time for single people to get public flats. 'They should be given more sympathy if living with parents is no longer an option for them,' she said.
HKU real estate Professor Chau Kwong-wing said the widespread trend towards the use of subdivided flats stemmed from something bigger, perhaps more political, than an ineffective housing policy.
'It is all about the inequality of wealth,' he said, 'Flats in urban areas are no longer affordable to a larger part of the population.'
But he does not agree that subdivided units should be eliminated, saying they 'have functional value, and it will just make people's lives more difficult'.
The ultimate solution, he says, is to restructure the economy and increase land supply. Only then will flat prices be curbed and people offered more jobs with opportunities.
Chau says determining the amount of land to be put on market requires a tactful strategy. Releasing too many sites could lead to a slump in prices, which touched a nerve for many Hongkongers.
'This is a political time bomb,' he said. 'But who is willing and able to defuse it?'
The number of buildings estimated to be more than 50 years old. Those at least 30 years old will be inspected once a decade