OFIS Arhitekti's Living Unit Stacks Three Timber Rooms at Ljubljana Castle

Three wooden rooms, each 4.5 meters long, stack into a slender tower at Ljubljana Castle with their angular ends pointing toward the city. The 2017 installation demonstrates Living Unit, a modular architecture system developed by OFIS Arhitekti together with partners C+C, C28, structural engineers AKT II, and contractor Permiz.

The whole idea starts small. One repeatable timber shell, designed for two people.

How big is one module?

Each basic module measures 4.5 meters long, 2.5 meters wide, and 2.7 meters high — roughly 14.8 by 8.2 by 8.9 feet. Two occupants get a double bed, wardrobe, table, and chairs, with provision for a bathroom and kitchenette. Those are compact cabin dimensions, not the proportions of a conventional apartment. Anyone expecting a flat in miniature will be disappointed.

The useful move is letting that first room become part of something larger. Modules connect horizontally or vertically, with combinations intended to house four to six occupants. A single cabin suits a short stay; several connected shells let the domestic functions spread out. The system offers different arrangements without demanding an entirely different building vocabulary.

Why the pointed ends?

The geometry does most of the character work. The module ends taper into truncated pyramids, glazed at their tips. AKT II explains that these projecting forms add internal storage space while expressing the structure's strength. From outside, the alternating projections make the stacked tower read as individual rooms rather than one uninterrupted shaft.

Behind that silhouette sits a prefabricated timber frame reinforced with plywood boards on both sides. The architects allow exterior and interior finishes to change according to context. The distinction matters: the repeated element is the structural shell, not a compulsory decorative package. Different sites need not receive identical-looking cabins simply because they share the underlying construction.

Ground connections adapt too. Steel anchors or removable concrete cubes secure the units instead of permanent foundations — useful where you can't, or shouldn't, pour concrete.

What is it actually for?

The team proposes holiday cabins, research accommodation, tourism, and shelter. These are intended applications, not proof that one specification performs equally well across every climate and terrain. A Slovenian hillside is not an Antarctic research station, and OFIS doesn't claim otherwise.

The castle installation adds another role: a temporary library, with books organized across its levels and nearby outdoor areas set aside for reading. It's a useful demonstration that the same shell can carry a public program rather than accommodation. The architecture supplies a small vertical destination within an existing landscape.

The trade-off in the section drawings

The drawings expose the compromise behind the tower's small footprint. Compact steps and ladders connect the levels, making circulation an active part of occupying the stack. Horizontal expansion would avoid that arrangement but require more ground — which, at a castle, is rarely on offer.

Living Unit's strongest proposition is this choice: repeat the room, then decide where the extra space should go. Up, sideways, or both.

By Amara Osei