This Indonesian House Turns Its Sloping Roof Into a Garden, a Staircase, & a Rooftop Pool

Some houses are designed to be looked at. Split Mass Residence, completed in 2026 by K-Thengono Design Studio, is designed to be moved through — a 712-square-metre home in BSD, South Tangerang, Indonesia, where every architectural decision is in service of movement, togetherness, and the slow pull of the outdoors.

Founder Kelvin Thengono built the project around a single, quietly radical idea: “The main design goal was to allow a seamless sequence of spaces that keeps the family connected, while also staying closely aligned with the surrounding landscape.” The house sits on a corner — what architects call a hook site condition — and rather than treat that exposure as a problem, the studio used it as the engine for the entire massing strategy. Volumes are split, pulled apart, and repositioned so that no single path through the house feels accidental.

Designer: K-Thengono Design Studio

That split is where the project gets interesting. Tiered, sloping garden roofs connect indoor living spaces directly to the planted outdoor setting, blurring the line between ceiling and garden in a way that feels more organic than architectural. From the open-plan kitchen, living, and dining area on the first floor, a glass door opens straight onto a grassy rooftop slope. An outdoor staircase continues upward to a swimming pool and barbecue area — the roof isn’t just a lid; it’s the social core of the house.

On the exterior, two materials do the heavy lifting. Concrete anchors the structure, giving it weight and presence on the streetscape. PE rattan panels wrap across the facade in woven screens that soften everything — filtering light, adding texture, and offering just enough visual privacy without closing the house off from its surroundings. The contrast is deliberate: one material says permanence, the other says warmth. Together they give the house a character that’s grounded and tactile rather than slick.

What Thengono has built here isn’t really a house in the traditional sense — it’s a system of encounters. Divided volumes, green roofs, and internal and external staircases create different scenarios for family interaction, so the architecture itself nudges people toward each other without ever forcing it. The rooftop garden crowning the whole composition reinforces that layered approach — landscape as architecture, architecture as landscape.

In a region where residential design often defaults to gated grandeur or tight minimalism, Split Mass Residence lands somewhere more considered. It’s a house that knows exactly where it wants you to be — and makes getting there feel like the whole point.

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Srishti Mitra
Srishti Mitra is a junior editor and a social media marketer at Yanko Design. After completing her Master’s in English Literature, her love for the written word led her to cover design and architecture, where she discovered a curiosity and admiration for both genres. She enjoys bridging the gap between the technical world of design, and the non-design audience through a simple, relatable, and fun format.