It is a common conundrum in Singapore: owners of semi-detached or terraced houses find themselves with land where the depth is multiple times longer than the width. ZIVY Architects’ latest project, located in Frankel Estate, is an example. Deep and narrow, with a ratio of four to one, the plot ran the risk of accommodating a residence that would mirror its profile, resulting in endless corridors and dark corners. 

In response, the husband-and-wife team that runs the firm, Loh Zixu and Evy Sutjahjo, knew they had to come up with what they termed as “a playful mix” of well-ventilated and bright spaces. The first idea they proposed was a pair of tapered voids open to the sky and incised into two different parts of the two-and-a-half-storey massing. This was later reduced to one to enable a larger bedroom. 

More interestingly, on the heels of this solution came the request for a flexible floorplan to allow the owners to easily reconfigure the house down the road. It therefore led to the inclusion of two massive pieces of off-form concrete walls that run the length of the house, containing the structural frame of the upper floors. This earned the project its name, Two Slices of Concrete. 

Maximising the flexibility of the floorplan

“These are the only structural elements in the house,” says Loh. “There are no other columns, so it is free in the middle.” Well, almost. Look at the floorplan and yes, while there are walls erected to make up the rooms, they are not load-bearing and can easily be demolished without compromising the building’s integrity. 

Sutjahjo adds that the owners were very particular about this request. “They told us since they did not maximise the GFA (gross floor area), they wanted to maximise the flexibility of the space. We then worked with the structural engineer to hide the columns within a minimal surface.”

The first “slice” of concrete makes up the façade of the house on the detached side, while the other is about two-thirds into the width. Rather than plaster and paint them over, the owners were comfortable with keeping them raw, with a grey, timber-textured surface. 

In doing so, the inward-facing sides become decorative too, with a feature-wall effect. For instance, the staircase is wrapped around it and the six residents come face-to-face with it on a daily basis when they move between floors. This meant that the finishing had to be executed well. 

ZIVY Architects made sure to start the planning of their casting early as they wanted the contractor to treat each as one standalone piece. The timber pattern had to wrap around it neatly across every edge, made possible through the use of six-metre-long rubber sheets to create the formwork. At times, the workers even had to touch it up by hand.

“The extra challenge for us was the fact that the formwork is interfacing with almost everything inside the house. It is also why we chose a pattern that was softer and had a more subtle texture to match the personalities of the owners,” points out Sutjahjo. 

A tapered void for light and air

To mitigate the narrow footprint of the 398.1sqm plot, they veered away from a homogeneous solution. “Essentially, it is the idea that we break the layout into digestible chunks,” says Loh. There is a mix of enclosed rooms and vestibules, sky bridge-like sections and a double-volume space. 

At the end is the tapered void that widens upwards and serves a variety of functions. The most basic is the letting in of natural daylight and ventilation to the back of the house. It also breaks the house into two wings, allowing for increased privacy for the residents of the rear rooms. 

“We really wanted to maximise the light. Because the owners were not insistent on having a maximum building footprint, we were able to introduce the tapered void,” explains Sutjahjo. 

The decision to vary its angle was made for two reasons, according to Loh, “Light comes in as a funnel and the ground floor needed more space, that’s why we made it narrower at the base. The result is as you’re walking along the length of the house, it does not feel like a long, dark space.”

Adding to the spatial vastness of the semi-detached house are the high ceilings and a double-volume space over the dining area, accentuated by a custom-designed cluster of matt, champagne-toned pendant lights. Another interesting space is the powder room on the ground floor, designed in a way that natural light filters in from a garden that sits above it and is open to the sky.

As in most homes, the living and dining rooms are on the ground floor. In the back is a bedroom for the family matriarch. The upper levels are occupied by bedrooms and study rooms. When the owners entertain, visitors get ushered to the attic floor where a roof-top terrace has been designed for this purpose. From the front of the house though, you’d never guess that it had any of these features – something which suits the residents, who are very private, just fine. 

In fact, the gentle grey tones of the sliding door frames and vertical aluminium screen by the common wall were purposely chosen to complement that of the two slices of concrete. Combined, the cool hue allows the house to sit quietly on the street, and in its own subtle way, hint at how behind its façade lies a home that is filled with everything light and bright.