Pencil tower

[6][7] It has become one of the most common types of buildings in the city, making Hong Kong the world's highest concentration of pencil towers.

The newer pencil towers on Manhattan's "Billionaires' Row" (a thin strip of Midtown near Central Park) are mostly supertalls.

The new designs were encouraged by an increase in the price of land and enabled by the use of elevators and steel frame construction which allowed buildings to be built taller.

[2] When the Equitable Building's shadow influenced the passage of a 1916 Zoning Resolution, street canyon shapes became regulated but 25% of the property was exempt.

This caused building designs of the era to have a wide base and thinner tower covering a quarter of the lot area.

[2] In the 1970s Hong Kong was in a similar position of high land values and lax zoning laws, and started building pencil towers.

[8] Multiple factors contributed: in 1964 the Hong Kong Housing Authority finished the Choi Hung Estate for 43,000 residents who suffered from a massive fire in 1953.

Developers needed to pay tens of thousands of HK$ for leasing each square meter (11 sq ft) of land.

These factors incentivized developers to build slender residential towers on small lots with one unit per floor.

[6][15][16] (US$0.55 million) Pencil towers became one of the most typical building types in Hong Kong, beside tong lau and cruciform apartments.

[9] Overall, buildings with a slenderness ratio of up to 18:1 have dominated the Mid-Levels residential district, making Hong Kong the "world capital" of pencil-thin towers.

In the 21st century Hong Kong pencil tower developments started to get much larger in scale than previous decades.

[4] A main challenge of super-slender buildings is the management of lateral movements due to wind loads, which can cause discomfort for occupants.

[21] Melbourne entered the global pencil tower scene with the construction of the Phoenix Apartments building that rose up on a 6.7-metre (22 ft) wide lot in 2013.

After oppositions from concerned neighbors, the design was revised down to 28 stories at a height of 88.5 metres (290 ft), still with a high slenderness ratio of 13.5:1.

Collins House incorporated many of advancements in technology including the first of such towers to use prefabrication of 3D structural elements to help navigate narrow project site.

If built, The Magic would become world's slenderest by a ratio of 26.6:1 based on the shorter side of its widths in a triangular footprint.

[26] The Skyscraper Museum cited Sky House (2008), a 55-story building made possible by a purchase of air rights from the Little Church Around the Corner, as an early example of New York's super-slender towers.