The Interlace Singapore: Stacked Blocks and Engineering

The Interlace Singapore is one of the most unusual housing developments in the world. Instead of a cluster of tall towers, it is made of 31 apartment blocks, each six storeys high, stacked on top of one another in a hexagonal pattern so that the whole complex reads like a woven, tilted village. Designed by Ole Scheeren with OMA and completed in 2013, it was named World Building of the Year at the World Architecture Festival in 2015.

Many people search for the development as a place to live or rent. This article is about its architecture and engineering: why the blocks are stacked, how such a structure can stand up, how the courtyards and terraces respond to Singapore’s climate and what the project means for high-density housing.

The project and the brief

The Interlace stands on a site of about eight hectares along Depot Road, near the Southern Ridges, on land previously occupied by the Gillman Heights condominium. The developer was a joint venture led by CapitaLand with Hotel Properties Limited. The brief called for around a thousand homes, and the completed project contains 1,040 apartments of various sizes.

The conventional answer to that brief in Singapore would be a set of slender towers, each isolated from the others, with landscaped ground in between. Scheeren, who began the project at OMA and completed it under his own practice after leaving in 2010, turned the tower on its side. The result is a set of horizontal blocks that interact with one another rather than standing apart. Readers who want the wider context of the practice can see our profile of OMA’s founder, Rem Koolhaas.

Thirty-one blocks in a hexagonal weave

Each block is a long rectangular bar, about 70 metres in length and six storeys high. The blocks are rotated and stacked so that they cross over one another, forming a hexagonal grid in plan with eight large courtyards enclosed between them. Stacking creates four main levels of blocks, and at three points the stacks rise to 24 storeys, forming peaks across the site.

Turning towers into stacked horizontal blocks changes almost everything about the way residents experience the building. The roofs of lower blocks become terraces and gardens for the blocks above. The undersides of upper blocks create shaded spaces over courtyards. Views open in many directions rather than in one. And the courtyards become large, distinct outdoor rooms, each with its own character, rather than leftover space between towers.

How the structure works

From an engineering point of view, the interlace singapore is closer to a set of bridges than to a conventional apartment block. In a typical tower, loads travel straight down through columns and walls stacked on top of one another from roof to foundation. Here, many blocks sit on the blocks below only at the points where they cross, and span the gaps between those points.

That means a block resting on others must carry its own floors over a long span, much as a bridge girder carries a deck between piers, and the blocks beneath must collect concentrated loads at the crossing points and take them down to the ground. The ends of upper blocks also project past their supports, producing large cantilevers that shape the silhouette of the complex. Structural engineers T.Y. Lin International, credited on the project, described it as drawing on their experience of both bridges and buildings, and the project received a BCA Design and Engineering Safety Excellence Award in 2014.

Load paths and stiffness

A structure like this has to be designed with great care for load paths, stiffness and long-term behaviour. Concentrated loads at crossing points require strong, stiff supports. Long-spanning blocks must be stiff enough that deflection and vibration remain acceptable for residents. Concrete creeps and shrinks over time, so differential movement between supported and spanning parts of the structure must be anticipated in the detailing of facades, partitions and services. The broad principles of carrying loads across gaps are covered in our guide to long-span structures.

Designing for Singapore’s climate

The stacked form is not only a structural and spatial idea; it is also a climatic one. Environmental studies of wind, sun and daylight shaped the arrangement of the blocks and the landscape. The blocks shade one another and the courtyards, reducing solar exposure at ground level. Openings between the blocks allow breezes to move through the site, and water features are placed in wind corridors where evaporation helps cool the air in outdoor spaces.

These are the core strategies of tropical architecture applied at the scale of a whole estate: shade, cross-ventilation, protection from heavy rain and generous outdoor living spaces. The development received the Green Mark GoldPLUS award from the Building and Construction Authority, a recognition of its environmental performance within Singapore’s green building framework.

Gardens in the sky

The roofs of the lower blocks are planted as gardens, terraces and communal spaces, and the courtyards are landscaped as distinct environments. Together they substantially increase the amount of green space available to residents beyond the footprint of the site, an idea in line with Singapore’s broader push towards landscape on buildings. The practical requirements are significant: planted roofs need waterproofing, drainage, soil depth and structural capacity for wet soil, trees and maintenance access. Our article on green roof design explains what those requirements involve.

For a development of this scale, roof landscapes also become shared social spaces. The design includes facilities such as pools, play areas and gathering spaces distributed through the courtyards and terraces, so that the complex functions as a village with many neighbourhoods rather than a single block with a central amenity.

Why The Interlace Singapore matters

The project challenges a deeply rooted assumption in high-density housing: that density means towers. By rotating and stacking blocks, it achieves comparable density while creating far more interaction between buildings, landscape and people. The 2015 World Building of the Year award, judged by a jury led by Sir Peter Cook, recognised that achievement.

It also demonstrates that unusual architecture places unusual demands on structure. Stacked, spanning and cantilevered blocks require the kind of thinking normally found in bridge design. In our consulting work, the same questions arise on any building where floors or volumes are supported off-grid: where the loads go, how stiff the spanning elements must be, and how the building will move over time.

Frequently asked questions

Who designed The Interlace in Singapore?

The Interlace was designed by Ole Scheeren with OMA, and completed under his own practice, Buro Ole Scheeren, after he left OMA in 2010, with T.Y. Lin International credited as structural engineer.

When was The Interlace completed?

The development was completed in 2013 and was named World Building of the Year at the World Architecture Festival in 2015.

How many blocks are in The Interlace?

There are 31 apartment blocks, each six storeys high and about 70 metres long, stacked in a hexagonal pattern around eight courtyards and rising to 24 storeys at three peaks, with 1,040 apartments in total.

How are the blocks of The Interlace supported?

Many blocks rest on those below only where they cross and span the gaps between, behaving much like bridges, with their ends projecting as cantilevers, which is why the engineers drew on bridge as well as building design.

Is The Interlace a green building?

Yes, it received the BCA Green Mark GoldPLUS award, reflecting design strategies such as mutual shading of the blocks, breezeways through the site, water features in wind corridors and extensive roof gardens.

Planning a building with transfer structures, long spans or planted roofs? Talk to our consultancy or get in touch.