Choi Hung Estate – Alternative to Demolition?

On 23rd March 2025, Geraldine Dening presented some of ASH’s proposals for alternatives to the demolition of the UK’s council housing estates and asked whether some of the strategies ASH proposed in the UK might apply in the Hong Kong Context at Choi Hung Estate.

See below the content of the lecture below:

Architects for Social Housing (ASH)’s argument against the demolition of London’s public housing estates was based on producing designs for the refurbishment and densification of 7 specific estates: Knights walk where we proposed an increase of over 200% new housing; Central Hill estate, nearly 50% new housing; West Kensington and Gibbs Green estates, 45%; Northwold estate, 45%; and St. Raphael’s estate, 80%.

These designs demonstrate that it is possible to increase the housing capacity on these estates between 45- 80% through infill and roof extensions. By selling or renting a proportion of these new homes on the private market, it is possible to generate all of the funds to refurbish the existing council homes, and improve the existing landscape and community facilities, while leaving the communities they currently house in place.

ASH’s most recent project for St Raphael’s estate, in North West London consisted of designs for an increase of around 80% of the housing, and improvement of the existing landscape and community facilities.

The new infill housing is shown here in yellow, with the roof extensions in pink. To the existing 760 homes we were able to add 608 new homes.

We commissioned quantity surveyors who established that all the construction and improvement works could be funded by the private sale or rent of around 50% of the new homes, with the remaining homes as homes for social rent (the lowest rent), enabling the continued existence of the existing community.

The centre of the estate has been run down for decades in what we describe as ‘managed decline’ where maintenance funds are withdrawn, and the social and communcal facilities and landscapes are allowed to deteriorate and decay, with associated negative effects on the ‘livibility’ of the estate and the welfare of the residents.

Our design  proposed a new social centre to the estate, with a new market place and community facilities, specifically aimed at supporting the existing residents, with low-cost rent for shared office or start up facilities, and no rent increases for the existing shops. This is because the effects of regeneration are fundamentally economic with increased rents and costs for existing residents.

In addition to proposing the additional housing, the designs also improved the public realm, landscape, commercial and communal spaces and facilities. Here, a new market is proposed in front of the existing refurbished shops.

The work also specified the refurbishment of all the 5 different building types on the estate.

The refurbishments would significantly improve the thermal performance of the existing homes, as well as replace all windows and doors, and update all the internal mechanical and electrical services, lowering heating costs, improving the living environment, and increasing the lifespan of the existing building by up to 60 years.

Structural engineers supported the proposals for the addition of two new lightweight prefabricated floors on top of the existing heavy reinforced concrete structure.

Environmental engineers calculated that the full demolition scheme proposed by the council’s architect would accrue four times as much embodied carbon as ASH’s infill and refurbishment scheme.

In addition an independent quantity surveyor assessed the financial costs of demolition and rebuilding to be three times as expensive per home.

A significant amount of the increase in housing density is due to the addition of two floors of roof extensions on top of the existing concrete framed buildings building (from the 60s and 70s).

The existing red concrete tiled roofs (added after initial construction) are heavy, and once removed the existing structure can easily accommodate the new extensions.

There are a number of existing highly acclaimed examples of retrofitting of existing estates across the world.

Lacaton, Vassall and Druot’s projects increase the size of the existing flats in many cases without the residents having to move out.

NL’s project demonstrates that the existing concrete framed structure can be reconfigured to accommodate a wide range of different flat configurations.

‘Rooftop housing developer Apex Airspace has revealed ambitious plans to build 10,000 ‘affordable’ homes in the next decade, using modular construction techniques’

‘Two 1950s-era residential blocks in Bermondsey, South-East London, have been extended upwards using innovative modular rooftop extensions to provide more “affordable” housing.

The infill scheme has effectively ‘grafted’ 30 new additional homes to the existing Antony and Roderick House, owned and managed by Lambeth & Southwark Housing Association (LSHA).’

Here we can see the completed roof extension in Southwark, south London, illustrated in planning above.  Two floors of lightweight prefabricated modules are erected on top of a 4-storey reinforced concrete frame with masonry infill. A slender exo-skeleton is visible which partially transfers the new loading to the ground.

Hong Kong’s Housing Authority’s extensive experience of building with prefabricated modules means adding new modular unit on top of the existing should be very straightforward.

Choi Hung’s shopping arcade is a successful modernist reinterpretation of the historic Hong Kong ‘Tong Lau’ and – I would argue  – a part of Hong Kong’s architectural heritage which should be celebrated, retained and refurbished

Existing  low-rise block

7 stories of reinforced concrete frame construction  with unoccupied flat roof

Double loaded corridor serving two types of  20-30 sqm flats overlooking adjacent courtyards and public realm

Ground floor is formed of an open colonnade providing shaded spaces for play as well as a successful shopping arcade or street,  which meanders through the estate providing a strong ‘backbone’ to the estate

New 3-4 floors of prefabricated lightweight roof extension

Potential for a range of different flat types/ sizes/ configurations/ heights.

New steel exo-skeleton to partially reinforce the existing structure if necessary, and take roof extension directly to the ground.

Existing flats to be refurbished:

New kitchens and bathrooms and services overhaul, with the potential for introducing light wells within the building depth.

Potential for new / refurbished façade/ balcony/ shading treatment to be associated with new structure.

On the right are illustrated the new modular blocks currently in production for the new public housing estates, and these are typically smaller than those currently occupied by the residents of Choi Hung.

Are residents expected to discard belongings in order to be able to comfortably occupy the new flats?

Double bedrooms are currently unable to accommodate double beds, whereas the layouts of the existing flats are more easily adaptable to a range of uses, layouts and occupants.