S-AR Stacks Three Apartments Inside an Open Concrete Grid Under a Palapa in Puerto Escondido

Casa Eva is a three-storey building on a ravine above the Pacific in Puerto Escondido, Oaxaca. Monterrey studio S-AR placed one apartment on each level, 540 m² in total. The program is modest. What sets the building apart is that the architects refused to build walls. A cast-in-place concrete frame, 12 by 15 metres on a 3 metre column grid, wraps the perimeter and defines the volume. The only enclosure comes from lightweight railings and translucent timber lattice boxes. A thatched palapa sits on top.

We find the project interesting because it treats structure and architecture as one decision. The grid works less like a skeleton waiting to be clad and more like a game board. Stairs, pools, kitchens, sunshades and storage are placed in it, around it and across it. The arithmetic is tidy: four bays by five, 180 m² per floor, three floors. Inside that discipline, each apartment turns out to be a different set of open terraces, each tuned to a different slice of canopy, mountain or sea.

A Gridded Frame Dropped into a Ravine

The site slopes toward the sea through dense coastal vegetation, with mountains behind. From a distance the building reads as one more thatched roof on a hillside that already has several. That modesty is deliberate. The palapa is the part of the building that belongs to the region, and S-AR lets it lead the silhouette.

Closer up, the frontal view shows how much is going on under the thatch. A white concrete frame lifts the roof clear of the treetops, and a round disc panel interrupts the orthogonal grid. Vernacular roof and rationalist frame are set side by side, and neither is softened to match the other.

Braces, Discs and a Stair Outside the Box

The elevated golden-hour view shows the frame's vocabulary clearly. Columns and beams set the rhythm, diagonal X-bracing appears where the structure needs it, and circular discs act as both screens and view-framers. A stone stair and a plunge pool sit at the edge of the grid rather than inside it, so the building's outline is never a clean box.

This is where the "spatial game" becomes visible from outside. Some elements live within the 3 metre bays, some slip out past the perimeter, and some cut across floors. The frame gives the order; the objects placed in it give the character.

The Grid as a Game Board

The study models make the concept almost diagrammatic. A timber-like cube of columns and beams holds cylinders, blocks and stacked floor plates, with a single diagonal brace on the lower level. You can read each solid as a service volume, a stair or a pool. You can also read the whole thing as a three-dimensional puzzle that still has room to move.

These interior volumes do more than hold bathrooms and storage. At critical points they help carry slab loads, so the pieces on the board are also part of the structure. That is a sharp move. The perimeter frame can stay thin and open because the furniture-scale volumes inside share the work.

Coffered Terraces as Living Rooms

The social areas in each apartment are covered terraces, not rooms with big windows. Under the coffered concrete ceilings, kitchens, daybeds and long dining tables sit in continuous open space cooled by ceiling fans and cross-breezes. The waffle slab does real climatic work: its deep coffers break up the light and give the ceiling texture without any applied finish.

The round, green-tiled plunge pool on one terrace shows the grid's flexibility at its best. It is a circle set into a square bay, a soft object inside a hard frame. Slatted timber cabinetry and red and coral upholstery warm the concrete, but the architecture does not depend on them. Clear heights of 2.85 m on most levels keep the spaces at domestic scale, while the ground floor reportedly gains extra height, about 4.05 m, where the slope drops away.

Lattice Boxes and a Framed Canopy

With so little enclosure, privacy falls to the timber lattice boxes around the bedrooms. They filter light rather than block it, and they turn afternoon sun into dappled patterns across floors and linen curtains. The sliding slat screen in the bedroom alcove is the most domestic moment in the building, and it is still semi-transparent.

On the terraces, the round wall discs frame the treetops so the view arrives already composed. Each apartment sits at a different height in the ravine, so one level looks into the canopy and another looks past it to the horizon. The same grid produces three different relationships with the landscape.

The Palapa as Crown

The top apartment trades the concrete ceiling for palm thatch on exposed timber rafters. The change in atmosphere is immediate: the space feels taller, warmer and more ventilated, and the pitched roof gathers light that the coffers below break apart. A hammock, a plunge pool and a long wooden table make it the most relaxed level in the building.

The palapa is more than a nostalgic gesture. It is a proven climatic tool on this coast, and it relies on regional craft that a concrete contractor cannot supply. Ending the strict grid with a soft, handmade roof is the building's best piece of judgement.

Plans and Drawings

The plans confirm how far the open-terrace idea goes. Each level is mostly one continuous space for living, cooking and dining. Bathrooms and storage are gathered into compact service volumes, and a spiral stair tucked toward the rear links the floors. The roof plan shows a hipped palapa with a central ridge opening, and the side stairs run along the edges.

The sections and elevation show the lowest level set into the slope, a circular opening in the lower wall, and the stepped stair following the hillside. The exploded axonometrics are the most useful drawings in the set. They pull the roof and the three floor plates apart and show each level as a different arrangement of partitions and circles inside the same column grid.

Why This Project Matters

Coastal Mexico has plenty of concrete-and-palapa houses, and many of them use the frame as a neutral support for glass. Casa Eva goes the other way. The frame is the architecture, and the openness is a result of its structural logic rather than a finish applied to it. Because service volumes help carry the slabs, the building can stay as open as the climate allows, and it relies on air movement rather than closing up against the weather.

For multifamily housing, the lesson is clear. A strict, repeatable grid does not have to produce repeated apartments. S-AR shows that a fixed 3 metre module can give three distinct homes, each shaped by its height in the ravine and by how its pieces are arranged. That balance of discipline and play is the part worth taking to other projects.

Casa Eva by S-AR, Puerto Escondido, Oaxaca, Mexico. Area: 540 m². Completed: 2026. Photography: Cesar Belio.

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