P+S Estudio de Arquitectura Builds a Concrete Impluvium in a Spanish Pine Forest

The Roman compluvium was a rectangular opening in the roof of an atrium, designed to funnel rainwater into a basin below. It was architecture reduced to a single elemental contract between sky and ground. P+S Estudio de Arquitectura borrows the name and the logic for a pavilion set inside a pine forest, where a tapering concrete volume rises from a carpet of ferns and channels light, air, and rain through a diamond-shaped oculus at its crown.

What makes this project worth studying is the deliberate collision of two material systems: a monolithic concrete shell that reads as geological from the outside, and a delicate timber frame on the inside that filters daylight through translucent fabric membranes. The pavilion is small, almost primitive in program, yet it operates with the precision of a full-scale building, complete with constructive details, structural bracing, and a clear tectonic hierarchy. It treats the forest not as scenery but as enclosure, letting the surrounding pines and ferns do the work that walls typically do.

A Concrete Monolith in a Sea of Ferns

The pavilion's exterior is uncompromising. Tapered concrete walls rise without ornament, their surfaces bearing the grain of formwork and the stains of weather. Seen from a distance, the structure barely registers among the tall pines, its grey mass absorbed by the muted palette of bark, moss, and overcast sky. The decision to use raw concrete here is not about brutalist posturing; it is about durability and indifference. The material does not compete with the forest. It simply occupies space within it.

The single entry is recessed and modest, a small doorway scaled to a child as much as an adult. There is no threshold ceremony, no portico. You arrive through ferns and step into concrete. The gesture is deliberately anti-monumental, ensuring that the forest remains the dominant spatial experience until the very last moment.

Threshold and Materiality

At the entry, timber meets concrete in an unresolved, productive tension. The door surround is constructed from rough-sawn wood, its warm tone cutting sharply against the cold grey shell. The junction is not seamless. You can read the gap between the two systems, understand that the timber interior is structurally independent from the concrete enclosure. This legibility is intentional. P+S treats the pavilion as a didactic object, where every connection tells you how it was made.

The faceted geometry of the concrete wall becomes apparent at the corners, where the formwork edges create subtle angular breaks. These are not decorative facets but the result of a casting process that accepts the constraints of flat plywood panels applied to a tapering form. The building wears its construction method on its skin.

Timber Frame and Filtered Light

Step inside and the material register shifts entirely. A skeletal timber frame rises within the concrete shell, its members joined with visible hardware and braced with diagonal struts. Translucent fabric panels stretch across the grid, converting harsh daylight into a soft, diffuse glow. The effect is closer to a Japanese shoji screen than to anything in the Western pavilion tradition. Light enters from all directions but arrives tempered, layered, almost textile in quality.

A timber ladder rises through the center of the frame, inviting vertical movement and reinforcing the idea that the pavilion is oriented upward, toward the sky opening. The metal hatch in the floor suggests a secondary relationship with the ground plane, hinting at drainage or storage below. Every element serves the core spatial proposition: a vertical tube connecting earth to sky, mediated by wood and cloth.

The Oculus and the Sky

The diamond-shaped roof opening is the pavilion's organizing element. Seen from below, it frames a square of sky through a lattice of converging timber beams, creating a geometric pattern that shifts with the angle of the sun. The aerial view confirms the purity of the move: a simple pyramidal roof punctured at its apex, sitting within a gravel clearing that acts as a ground-level compluvium, collecting rainwater that runs off the tapered walls.

The interplay between the woven fabric screens and the timber grid produces a moiré effect when light passes through at shallow angles. In the afternoon, the interior becomes a study in overlapping shadows, with each layer of structure casting its own pattern onto the next. The result is spatial depth generated not by volume but by material transparency.

Textile Screens and Atmospheric Control

The translucent panels are not uniform. Some appear woven, others stretched taut, and the variation produces a range of light conditions within a single interior. Afternoon sun hits the southwest face and illuminates the diagonal bracing in warm amber tones, while the opposite wall remains cool and shadowed. The pavilion becomes a sundial of sorts, its interior atmosphere calibrated by orientation and time of day.

Outside, where the black fabric wraps the eave, the material choice shifts to opacity, protecting the timber structure from direct weather exposure. The rough post sitting in a bed of dry leaves reads as almost provisional, a detail more common in temporary installations than in permanent buildings. This ambiguity between permanence and impermanence is one of the pavilion's quiet strengths.

Plans and Drawings

The drawing set reveals the rigor behind what could otherwise pass as a simple shelter. The exploded axonometric is the most instructive: it breaks the pavilion into discrete layers, showing the gridded roof panels, the angled rafter assembly, and the independent timber frame as distinct tectonic episodes stacked within the concrete shell. The constructive details of beam intersections and column connections demonstrate a level of joinery ambition that elevates the project well beyond carpentry.

The early sketches, rendered in pen and orange crayon, are worth lingering over. They show the pyramidal volume already fully resolved in concept, with internal triangular bracing and vertical slats that would eventually become the fabric-wrapped grid. The physical model, photographed against black, confirms the pentagonal geometry at the base and the way the structural frame flares outward before tapering to the roof. This is a project where the idea arrived early and the detailing caught up.

Why This Project Matters

Pavilion architecture often suffers from a surfeit of ambition and a deficit of rigor. Temporary structures get treated as sculptural provocations, excused from the discipline of real construction. The COMPLUVIUM Pavilion goes the other direction. It takes a small, single-room program and subjects it to the same tectonic scrutiny you would apply to a house or a museum. The result is a building that rewards close looking: every joint, every material transition, every relationship between structure and skin has been considered and resolved.

More broadly, the project is a quiet argument for typological memory. The compluvium is not a metaphor here; it is a functional strategy, a way of organizing a roof around a central void that admits light and water. By reaching back to a Roman domestic technology and rebuilding it in timber, concrete, and fabric within a contemporary forest, P+S Estudio de Arquitectura demonstrates that architectural innovation does not require novelty. Sometimes it requires recognition: seeing an old idea clearly enough to build it again, better.

COMPLUVIUM Pavilion by P+S Estudio de Arquitectura. Photography by P+S Estudio de Arquitectura and Javier Callejas.

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