Petronas Towers Case Study: Plan, High-Strength Concrete and Skybridge (César Pelli)

The Petronas Towers in Kuala Lumpur are two 88-storey office towers by Cesar Pelli & Associates, engineered by Thornton Tomasetti and built in the mid-1990s for Petronas, Malaysia's national oil company. For a studio or thesis case study they teach four things clearly: a plan grown from simple geometry, a very tall structure in high-strength concrete rather than steel, a bridge joining two towers that sway separately, and deep friction piles on difficult ground.

Petronas Towers at a glance

• Architect: Cesar Pelli & Associates (now Pelli Clarke & Partners), design principal César Pelli; associate architect Adamson Associates.

• Structural engineers: Thornton-Tomasetti Engineers with Ranhill Bersekutu (engineer of record).

• Builders: Tower One, a joint venture led by Hazama Corporation; Tower Two, a joint venture led by Samsung Engineering & Construction.

• Client: KLCC Holdings, majority owned by Petronas.

• Location: Kuala Lumpur City Centre (KLCC), on the former Selangor Turf Club racecourse.

• Dates: competition 1991; excavation from 1993; first staff moved in January 1997; official opening August 1999. Completion is 1997 for the architects, 1998 for the CTBUH.

• Size: 451.9 m to the architectural top, highest occupied floor 375 m (CTBUH), usually rounded to 452 m; 88 storeys. Gross area 218,000 m² per tower (Aga Khan review) or 197,500 m² for Tower 1 (CTBUH).

• Status: offices; skybridge and observation deck open to ticketed visitors. Aga Khan Award for Architecture, 2004.

Most figures are from the Aga Khan Award's On-Site Review Report by Galal Abada (May 2004), which drew on the architects' records and interviews with Pelli and the client. Where sources disagree, both figures are given. Diagrams are MOA's own schematics, not copies of the architects' drawings.

Why were the Petronas Towers built? The brief and the client

In 1981 Malaysia's government decided to move the racecourse out of central Kuala Lumpur and build a new city centre on its 100 acres. A 1990 master plan by Klages, Carter, Vail & Partners set out a mixed-use "city within a city" around a 50-acre park. This account, and most figures below, come from the Aga Khan Award On-Site Review Report (2004), the most detailed public record of the project.

In June 1991 eight firms were invited to design the towers, including Kohn Pedersen Fox, Murphy/Jahn, Aldo Rossi and Cesar Pelli & Associates. The brief asked for a place "that people can identify as unique to Kuala Lumpur and Malaysia", with offices and a twin-tower hotel; Pelli's team made both towers offices. Petronas's chairman told the reviewer that the other entries "looked as if they could be built anywhere". Pelli, in a 2005 interview published by ArchDaily (Vladimir Belogolovsky, 2019), recalled being asked "to design a Malaysian building" and wondering what that could mean.

Site and context: the Golden Triangle and Kenny Hill

The towers sit at the north-west corner of KLCC, in a business district the review says grew without a master plan and "lacks a distinctive urban form". Kuala Lumpur is about 3° north of the equator: hot, humid, sunny and wet, with no seismic activity or typhoons.

The ground was the hard part. Under the flat site lies limestone weathered into caverns and ravines, overlain by a stiff soil called Kenny Hill. Late borings found the rock sloping steeply under the planned positions, so both towers were moved about 60 m south-east, which also created the formal garden in front. For documenting a site like this, see our guide to doing an architecture case study.

The twin towers by Cesar Pelli & Associates, completed in the late 1990s, with the skybridge at levels 41 and 42 and the stepped crowns that taper to steel pinnacles. Photo: Marcin Konsek, CC BY-SA 4.0, via Wikimedia Commons

Petronas Towers design: concept and ideas

Pelli's own account starts with culture. "I needed to dig deeply into Islamic culture, and we tried to capture the feelings of Islamic art," he told The Talks (2017). Among his main design features the review lists a floor plan using simple geometry to express Islamic culture and art in Malaysia. The Skyscraper Museum quotes his aim of a monument "not specifically Malaysian, but will forever be identified with Kuala Lumpur".

The second idea is the pair. Pelli told Belogolovsky he arrived at "two identical buildings in a symmetrical setting", with a figurative space between them joined by a bridge; the review notes the bridge was not in the brief. Height came last: in June 1993 the design stood at 432 m, and at the client's request to beat the Sears Tower the spires were stretched to 451.9 m (Aga Khan review). The New Straits Times (2020) gives the original plan as 427 m. Thornton Tomasetti says the towers were the world's tallest until Taipei 101 in 2004.

Petronas Towers floor plan: from an eight-pointed star

The plan begins as two interlocking squares, one turned 45 degrees, making an eight-pointed star. Eight semicircles in the inner angles add floor space, giving 16 bays: eight points and eight lobes (Aga Khan review). The architects' project page says the star stands for unity, harmony, stability and rationality. An early scheme had a twelve-pointed star; the review says it changed after the prime minister observed that it was "more Arabic than Malaysian". Pelli was also asked to orient the towers towards Mecca, which was not his intention.

A square core of about 23 m by 23 m holds lifts, stairs, shafts and toilets. Steel beams span to a ring of 16 concrete columns, and the bays cantilever beyond it in steel. A round annex, the "bustle", rises 44 storeys on one side of each tower. Usable area is about 70% of a typical floor and the core about 23%, which Pelli called "a good ratio for very tall buildings".

Two squares make a star, eight semicircles add floor space, and a ring of 16 concrete columns around a square core carries it. Schematic, not to scale. Diagram: MOA

This is MOA's schematic from written descriptions. For the real master plan, typical floor plans and section, see the architect's presentation panels in the Aga Khan Award project file on Archnet.

Petronas Towers structural system: high-strength concrete

The engineers chose concrete, not steel, for everything that stands up. The review describes a "soft tube": 16 cylindrical columns of high-strength concrete, nearly 2.4 m across at the base, tapering and leaning inwards as they rise, linked by slightly arched ring beams and tied to the core by concrete outriggers at levels 38 and 40. Floors are steel beams under concrete-filled metal deck.

Charles Thornton's American Concrete Institute paper, High-Strength Concrete for High-Rise Towers (1994), gives the concrete as 40 to 80 MPa cube strength and cites its damping and lateral stiffness. The review calls it the first use of Grade 80 concrete in Malaysia and gives practical reasons: local crews knew concrete, it simplified awkward joints, it gave fire-rated core walls and it reduced sway. The steel floors could be made locally, erected fast and altered for tenants. The structure was designed for 135 km/h winds.

Petronas Towers construction: two contractors, one tower each

The review lists the Mayjaus joint venture (Hazama, JA Jones, MMC, Ho Hup, Mitsubishi) for Tower One and the SKJ joint venture (Samsung, Kukdong, Syarikat Jasatera) for Tower Two; the New Straits Times adds that Samsung's team built the skybridge. Samsung's project page says its tower rose about 4.5 days per floor, with verticality checked daily by GPS. Popular accounts of a "race" disagree on who finished first; we found no primary source that settles it. Excavation began in April 1993, the superstructure in April 1994 and the skybridge in July 1995, and the pinnacles were jacked up in March 1996.

Petronas Towers skybridge: a bridge that moves

The two-storey skybridge joins the sky lobbies at levels 41 and 42. The review gives a 58.44 m centre-line span, 170 m above the street. Thornton Tomasetti says "more than 150 m" and Samsung's newsroom 177 m, so quote height with its source.

Two towers this tall sway differently, so a rigid link would be torn. The answer was a two-hinged arch: steel legs spring from level 29 of each tower at 63 degrees and meet under mid-span. Spherical bearings at the feet rotate, a pin at the crown lets the middle rise and fall, and the bridge ends slide. When the towers move apart the legs flatten and the bridge dips. The review adds that without the arch the bridge would deflect but not fall, and that as a protected route between towers it saved two extra fire stairs.

The skybridge rests on two steel legs that meet under its centre: hinged at their feet and at the crown, they let the towers move independently. Photo: Marcin Konsek, CC BY-SA 4.0, via Wikimedia Commons

Petronas Towers foundation: friction piles on uneven rock

Each tower weighs about 300,000 tonnes. On a plain mat it would have pressed on the soil at 1,140 kPa, more than twice what Kenny Hill can carry (Aga Khan review). Instead each sits on a 4.5 m thick raft over 104 barrettes, rectangular cast-in-place piles up to 1.2 m by 2.8 m and 40 m to 105 m deep. They work by friction, and their lengths vary to keep settlement even over the sloping limestone. The largest raft pour was 13,200 m³ over 54 hours. A 2001 article in USC's Illumin gives depths of 55 m to 130 m; we use the review's figures.

Concrete core and columns carry each tower; the skybridge sits on a hinged arch so the towers can sway independently; friction piles of varying depth hold the rafts above sloping rock. Schematic, not to scale. Diagram: MOA

Materials and the facade

The towers are clad in stainless steel and 20.38 mm laminated light-green glass, about 33,000 storey-high panels, with "bullnose" and "teardrop" sunshades that read as silver bands. Each tower ends in a 73.5 m, 176-tonne steel pinnacle; the review lists conical tops inspired by stalactites among Pelli's design features. Inside, the lobbies use Malaysian timber, and the marble floor pattern comes from pandan weaving. More than 60% of materials were sourced in Malaysia.

Light, climate and services

The towers are sealed and air-conditioned, so the climate response is shading and efficient plant. The review's appendix says the sunshades were optimised to cut solar gain by about 15%, and single glazing was chosen on operating cost. Chilled water comes from a 30,000-ton district cooling plant with gas cogeneration. The review states that exhaust-air heat recovery cuts air-conditioning energy by 50%, without measured data, so treat that as a claim. It also found some offices short of daylight.

Reception: what users, critics and the architect said

The towers won a 2004 Aga Khan Award, but the review behind it is not uncritical. It found the offices flexible and well kept, but the complex poorly integrated with nearby towers and highways. "This really was a problem," Pelli told the reviewer, saying his master plan changes were rejected for commercial reasons. A road also splits the front garden, leaving one half almost derelict.

No audited cost is public. The review cites reports of USD 800 million, KLCC sources saying USD 1 billion for the towers, and Pelli saying USD 800 million "could be the total cost"; it estimated about MYR 500 per m², against MYR 220 to 300 for typical local towers. The New Straits Times gives RM1.6 billion. We have not converted these to rupees, since a conversion would ignore decades of inflation.

What designers in India can take from it

This is our reading, not a code rule.

• Choose a structure your builders can make well. Concrete won here partly because local crews knew it and local industry could make Grade 80, with steel kept for floors where speed mattered. Ask the same of an Indian supply chain before fixing a tall frame.

• Pay for ground investigation early. Late borings moved two 88-storey towers 60 m. Indian ground varies as sharply; our post on foundations on black cotton soil makes the same point at house scale.

• Shade the glass before cooling it. External sunshades and efficient central plant did the work here. Our guide to green building certification and the energy code sets out what Indian rules expect.

• Make one element do two jobs. The skybridge is a symbol, a link and an escape route. Indian fire rules set their own requirements for refuge areas and stairs, so test such ideas with a fire consultant.

For a tall-building thesis, see our B.Arch thesis topics by typology.

Visiting the Petronas Towers

The towers are offices, but the skybridge and observation deck are open to visitors. The official PETRONAS Twin Towers eTicket site says visits use timed tickets, sold first come, first served, and asks visitors to arrive 15 minutes early; check it for current days and times. The concert hall, Suria KLCC mall and KLCC Park sit at the foot of the towers. For more buildings, see projects by MOA members.

FAQ

Who designed the Petronas Towers?

César Pelli of Cesar Pelli & Associates (now Pelli Clarke & Partners) won the 1991 competition, with Adamson Associates as associate architect. Thornton-Tomasetti Engineers and Ranhill Bersekutu were the structural engineers.

When were the Petronas Towers built?

Excavation began in April 1993 and the superstructure in April 1994. Petronas staff moved in from January 1997 and the official opening was in August 1999. The architects give completion as 1997, the CTBUH as 1998.

How tall are the Petronas Towers and how many floors do they have?

451.9 m to the architectural top (usually rounded to 452 m), with the highest occupied floor at 375 m, according to the CTBUH Skyscraper Center. Each tower has 88 storeys above ground.

What is the structural system of the Petronas Towers?

A high-strength concrete core and a ring of 16 concrete columns linked by ring beams, tied together by outriggers at levels 38 and 40, with steel floor beams. Each tower sits on a 4.5 m piled raft on 104 friction piles.

How much did the Petronas Towers cost?

No audited figure is public. Reports cited by the Aga Khan review range from USD 800 million to USD 1 billion for the towers; the New Straits Times gives RM1.6 billion.

Find an architect for your own project on MOA: browse architects.

Sources

• Aga Khan Award for Architecture (via Archnet): Petronas Office Towers project file, including the On-Site Review Report by Galal Abada (May 2004) and the architect's presentation panels (accessed 4 Nov 2026)

• CTBUH Skyscraper Center: Petronas Twin Tower 1 (accessed 4 Nov 2026)

• Thornton Tomasetti: Petronas Twin Towers (accessed 4 Nov 2026)

• American Concrete Institute: C. T. Thornton, High-Strength Concrete for High-Rise Towers, SP-149, 1994 (accessed 4 Nov 2026)

• Pelli Clarke & Partners: Petronas Towers (accessed 4 Nov 2026)

• The Skyscraper Museum: Petronas Towers, Supertall! (2020) (accessed 4 Nov 2026)

• The Skyscraper Museum: Petronas Towers, tallest towers (accessed 4 Nov 2026)

• The Talks: César Pelli: "One aspires for the sky", Emma Robertson, 22 March 2017 (accessed 4 Nov 2026)

• ArchDaily: In Conversation with César Pelli, Vladimir Belogolovsky, 22 July 2019 (accessed 4 Nov 2026)

• New Straits Times: NST175: Standing tall in the eyes of the world, Teoh Pei Ying, 4 September 2020 (accessed 4 Nov 2026)

• Samsung C&T: Petronas Tower, Kuala Lumpur (accessed 4 Nov 2026)

• Samsung C&T Newsroom: Reaching high in Malaysia, 8 April 2020 (accessed 4 Nov 2026)

• Illumin, University of Southern California: The Petronas Towers, Brandi Henry, 2001 (accessed 4 Nov 2026)

• Aga Khan Development Network: Seven projects receive 2004 Aga Khan Award for Architecture, 27 November 2004 (accessed 4 Nov 2026)

• PETRONAS Twin Towers: official eTicket site (accessed 4 Nov 2026)