‘Casa Trevo’ or ‘Trefoil House’ is a two-storey residence, located south of Lisbon, Portugal. The site’s close proximity to the Atlantic Ocean provides pleasant breezes and plenty of sunshine, across all seasons. The project sits in a forest of pine trees, rising tall above a sandy terrain.
▼项目外观，external view of the project ©Fabio Cunha
Inside, the rooms are organized around three outdoor patios, circular in shape. They function as extensions of the interior spaces as well as being light wells and large openings for the living quarters below and sleeping rooms above.
▼圆形中庭作为空间的延伸，circular patios augmented materiality
The nine-meter high patios also perform as main structural voids in the form of three hollowed and semi-open columns. Together, they support a series of floor slabs ascending at different increments. They also hold a beam of water, serving as a lap pool on the rooftop and whose underbelly is pressing down on the spaces below.
▼主要结构示意，primary structure disgram
The structure is made of cast-in-place concrete and plays off the ambiguity of mass and void and of inside and outside. It addresses the site by stepping the ground plane along its natural slope and by bringing that level difference inside. It is anchored into the ground firmly but irregularly around its perimeter vis-à-vis the terrain.
▼项目鸟瞰，aerial view of the project ©Marco Antunes
▼建筑外侧顺应地势，the perimeter of the house following the terrain ©Fabio Cunha
‘Casa Trevo’ exerts a peculiar sense of autonomy and monumentality, despite its small size. It is unified by concrete on the outside, subverting the perception of its scale, while serving as canvas for a dialogue between nature and architecture to be projected. It also exudes a solid impression of mass while revealing little of its inside. The house produces its own introverted world facing the sun, with private yet mutable spaces rendered intermittently by Lisbon’s brash light.
▼有纪念感的建筑，从外部无法看到室内空间，house wwith monumentality, little interior could be seen from outside ©Fabio Cunha
▼屋顶泳池，roof top swimming pool ©上：Marco Antunes，下：Fabio Cunha
CONTRASTING SCALES (on scaling up and down)
▼混凝土表面和体块研究，exposed concrete surface and volumetric studies
In order to produce scalar shifts in the spatial disposition of the house, elements of different sizes are introduced to its massing. Some are more vertically pronounced, while others horizontally arranged to form an integrated concrete monolith of multiple notations of scales. Moments of tensions and compressions emerge as a result, creating, internally and externally, a range of dynamic and varied experiences of space.
▼透过客厅看向东侧露台，view through the living room to the east patio ©Fabio Cunha
▼透过餐厅看东侧露台，view through the kitchen to the east patio ©Fabio Cunha
GROUNDED SKY (on ground: response to site)
One of the design intents was to raise ground as roof and insert the space of the house under it, while keeping the terrain as untouched and natural as possible. By elevating the ground plane to the roof datum, a latent space is left open beneath for an exploration in section to take place. A duality between literal and conceptual ground establishes a first hierarchy between horizontality and verticality.
▼从不同方向看向屋顶楼板，roof plat ab
VOIDED STRUCTURE (on structure: vertical)
The structural imperative caused by lifting the ground towards the sky prompts an ensuing architectural idea for the house; the potential for an added experience of space provided by the inhabitation of its main structure, material and resulting forces. To this effect, three sizeable primal elements are introduced to support a newly defined roof-scape. This tripartite arrangement asserts the vertical axis as the major structural element, consequently liberating the slab.
▼东侧露台，设有通向下方客厅和上层卧室的开口，east patio with openings connecting to the living room below and bedroom above ©Fabio Cunha
SHATTERED SLAB (on slab: horizontal)
▼楼板与流线，slabs and circulation ©Fabio Cunha
As walls come first, floor slabs are made second and independent from their traditional and rigid building sequence: slab, wall, slab, etc. Disintegrated into bits that are more attuned to their specific room sizes, the dominance of the horizontal datum has at last made way for a variety of volumetric spaces.
▼从客厅看向入口和厨房，view to the entrance and the kitchen from the living room ©Fabio Cunha
▼从客厅看向中庭里的入口，view of the entrance inside the atrium from the living room ©Fabio Cunha
▼下方是厨房，上方是卧室的空间，space with kitchen below and bedroom above ©Fabio Cunha
▼中庭连接卧室和客厅，atrium connecting bedroom and living room ©Fabio Cunha
▼卧室，上方是泳池体块，bedroom with swimming pool volume above ©Fabio Cunha
▼向上看中庭空间，楼板形状富于变化，look up from atrium space, plates in various sizes ©Fabio Cunha
PLAIN GEOMETRY (on geometry: plan)
The role of geometry in the work is procedural and non-compositional; it is dynamic but not graphic. A relational framework serves as a regulatory plan diagram, a basis from which all parts relate and are integrated into a coherent whole. It is prescribed yet agile in adapting to various design evolutions until a solid formation is reached.
▼客厅，living room ©Fabio Cunha
▼卧室，bedroom ©Fabio Cunha
▼卫生间，bathroom ©Fabio Cunha
MASKED FAÇADE (on façades: openings)
The house doesn’t take any posture towards its site. There are no privileged vistas, no distant horizon and no strict physical boundaries to address; no front, back or side divisions. In place, it negates its context by vertically addressing its immediate environment. The sky is the site’s only vantage point, affirming the rooftop datum as the only façade for the project.
▼西侧露台，west patio ©Fabio Cunha
▼向天空打开的空间，space open to the sky ©Fabio Cunha
SUPERFICIAL MASS (on massing: volume)
To render the spatial and scalar concepts active in the house, an important design consideration was to retain the reading of the overall built mass. As little visual interference as possible had to be sustained in order to avoid the breaking down of volumes into disparate planes and surfaces. The detailing strategy adopted was to erase any presence of details or visual breaks which could distract from the perception of a holistic monolith.
▼体块表面连续完整，the mass presenting a holistic monolith ©Fabio Cunha
CURTAINED WALL (on wall: detail)
▼露台墙面细部，details of the patio wall
The provision of blank canvases inside the elemental patios makes room for something more intricate to occur at a detail scale. Progressively folding in and out of the wall thickness of the patios, and calibrated to the specific lighting context, concrete corrugations are made into devices that delay the passage of time through a game of light and shadow.
▼波浪形墙面形成独特的光影，unique light and shadow created by corrugated concrete ©Fabio Cunha
INSIDE OUT (on space: interiority)
A series of photographs and films were commissioned to serve as an independent house study. They search for the first time how pure structure could become absolute space and vice-versa. Prior to inhabitation, they survey the existential qualities of the house created by the sole participation of natural sunlight with material, structure, mass, scale and space.
▼夕阳下的建筑，building under the sunset ©Fabio Cunha
▼夜景，night view ©Marco Antunes
▼一层平面图，ground floor plan
▼二层平面图，first floor plan
Architect: Olivier Ottevaere & Elsa Caetano (www.doubleostudio.com)
Local architect: Marco Antunes
Structural Engineer: Joao Silva
Contractor: CS Construtora
Location: Aroeira, Portugal
Completion Date: 03/2020
Gross Floor Area: 300 sqm