By the 1970s, as more people resettled from attap houses to flats, the HDB switched gears from rushing to house a nation to providing people with more than just a roof over their heads.

As the HDB gained experience and confidence, block designs took on more variations in shape, height and features.

Blocks were designed to make the most of topographical features — such as slopes and bends in the lay of the land — while still adhering to the basic principles of good housing.

Compared with flats built in the previous decade, those built in the 1970s had better designs, improved toilets, storerooms and wider corridors.

As flats took on a different look, so did the block shapes. In addition to the traditional rectangular slab blocks, newer blocks took on interesting shapes such as L, U, Y, square and point blocks.

Many of these blocks, with their distinctive designs, have since become iconic landmarks of the towns they are located in.

The point block design has two main advantages over that of the slab block.

By eliminating common corridors and placing flats on the four corners of every floor, the point block design allows each flat to have windows on up to three sides for ample lighting and cross-ventilation.

In addition, it offers greater privacy as no windows open onto common areas.

The demand for larger flats also increased. Between the 1970s and 1980s, HDB started to develop flat types such as four- and five-room flats.

We previously reported on how the interior of HDB homes has changed over the decades. Read more about it here.

Along the way, some blocks were built as a combination of a slab and a point block, such as Rowell Court in Little India, which was completed in 1982.

The slab blocks are made up of mostly three-room flats, while the point blocks are made up of either four- or five-room flats. In the 1970s, point blocks were also more expensive to build, which meant that only upper middle-class families could afford them.

Combining both the slab and point block, and thus flat types, into a single block provides more opportunities for families of different social classes to become neighbours.

It also offers an interesting skyline and provides visual relief, says Dr Liu.

To ensure residents are well-served with amenities, town centres are built at the geographical centre of a town, with neighbourhoods ringed around it.

Each neighbourhood — accommodating about 4,000 to 6,000 flats — is served by a neighbourhood centre with food outlets, provision shops, community centres and other facilities.

One level below the neighbourhood is the precinct, which is about 3ha to 4ha, says Dr Liu.

Each precinct of about 600 to 800 units is clustered around shared facilities such as open areas or commercial spaces.

The size, scale, layout and design of precincts is such that residents could share common facilities such as children’s playgrounds and courts for various sports.

Distinctive features, including in the street furniture, and new building designs are introduced at both the town and precinct levels.

The precinct, which is unique to Singapore, was born out of the desire to foster a sense of community and identity, says Dr Liu.

Toa Payoh, developed in the 1960s, is HDB’s first comprehensively planned satellite town.

Ang Mo Kio, Bedok and Clementi towns followed soon after, offering residents mixed-use developments that allow a “live-work-play” environment.

In the 1980s and 1990s, added emphasis was placed on strengthening town identity.

Towns built in this period include Bishan, which has red-brick and pitched roof blocks; Potong Pasir, which has sloping rooftops; Sengkang, which has marine motifs such as stilt-like structures on block facades; and Pasir Ris, which has blue and white pitched roofs.

Colour is one cost-effective way to differentiate HDB blocks, says Mr Soh. Some towns have used paintings and murals to much greater effect than others.

For instance, there is an often-photographed TV test pattern block in Tampines Street 42 and a rainbow block in Hougang Avenue 7.

Architectural historian Chang Jiat-Hwee says block painting also serves a basic function — it is great for keeping algae at bay in Singapore’s tropical climate and helps to maintain a certain image of the block.

Mr Soh and Mr Chang, along with design writer Justin Zhuang, co-authored Everyday Modernism: Architecture & Society In Singapore. The book’s 33 essays and more than 100 photos provide insights into and celebrate Singapore’s modernist architecture.

Geometric shapes are another popular way to differentiate precincts. It is most common in blocks built in the 1990s, when Singapore entered a period of “post-modernism”.

These motifs, which are on block facades, are largely decorative with little to no functional purpose. But they allow residents to tell others exactly where they live based on the motifs, which form a sense of identity.

Up to that point in time, public criticism was that modernist architecture — with its functional and utilitarian nature — was bland and standardised, says Mr Zhuang.

These motifs, along with the wave of post-modernism architecture – an eclectic, irreverent style of architecture – seek to deliberately rebut that, to show that public housing can be different, he adds.

Architects also took inspiration from local heritage objects. In Hong Lim Complex, the pitched roofs and arches pay homage to the shophouses in the surrounding area.

Each HDB town also looks different, depending on when most of its blocks were built. For example, Toa Payoh has a mix of blocks built in different decades. When you step into Toa Payoh, you will find blocks completed in the 2010s and several old slab blocks completed in the 1960s with units on the ground floor.

On the other hand, most blocks in Pasir Ris were completed in the 1990s – which was the post-modernist era when the HDB was experimenting with geometric shapes.

Singapore’s HDB towns have different growth periods. We look at the number of blocks built each year, split by town.