OFIS architects renovates boathouse in slovenia with rooftop garden that filters lake water

OFIS Architects crowns timber structure with filtration garden

Along the western edge of Slovenia’s Lake Bled, OFIS Architects revitalizes Boathouse Zaka, a 25.5-square-meter timber-clad structure. While its humble exterior reflects the vernacular scale and materiality of alpine lakeside buildings, the project introduces an experimental rooftop filtration garden, turning the boathouse into both a scientific facility and an educational device. 

A series of wooden trays sits atop the pitched roof, filled with layers of stone, gravel, sand, and soil, and planted with native alpine flower species. Lake water is pumped through this substrate, slowly filtering as it irrigates the vegetation, mimicking natural water purification processes. The filtration beds on the roof are part of a scientific experiment and a didactic tool. In this way, the roof becomes a public-facing interface of ecological care, visibly performing the environmental purpose of the building. 

all images by Miran Kambic

boathouse zaka adopts a skin that breathes in slovenia

Ljubljana-based OFIS Architects focuses on revitalization through reuse, dismantling, and restoring the original timber frame and cladding. This restoration preserves the proportions and spatial rhythm of the existing structure while grounding it in local craft traditions. The original facade is reinstalled as a series of rotated and offset wooden planks, creating a skin that breathes. This semi-transparent cladding filters light, air, and views, allowing the structure to become ‘a filter rather than a wall,’ as the team notes.

Boathouse Zaka stores two research boats used for environmental monitoring of Lake Bled, whose crystal-clear and heavily visited waters require continuous observation. Material interventions, such as replacing cold cement tiles with natural wooden flooring, improve internal comfort for researchers and maintain the structure’s coherence with its timber envelope. 

As climate pressures and tourism intensify around Lake Bled, the project suggests that future-forward architecture may not require elaborate forms but regenerative gestures that restore, teach, and protect. 

OFIS Architects revitalizes Boathouse Zaka

a 25.5-square-meter timber-clad structure

a series of wooden trays sits atop the pitched roof

lake water is pumped through this substrate

located along the western edge of Slovenia’s Lake Bled

the original facade is reinstalled as a series of rotated and offset wooden planks

Boathouse Zaka stores two research boats used for environmental monitoring of Lake Bled

OFIS Architects focuses on revitalization through reuse

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the filtration beds on the roof are part of a scientific experiment

the project suggests that future-forward architecture may not require elaborate forms

this restoration preserves the proportions and spatial rhythm of the existing structure

this semi-transparent cladding filters light, air, and views

replacing cold cement tiles with natural wooden flooring improves internal comfort

grounded in local craft traditions

the humble exterior reflects the vernacular scale and materiality of alpine lakeside

detail | all technical drawings by OFIS architects

facades

plans

sections

site plan

project info:

name: Boathouse Zaka

architect: OFIS Architects | @ofis_architects

location: Lake Bled, Slovenia

site area: 47 square meters

built area: 25.5 square meters

client: Environmental Agency of the Republic of Slovenia

design team: Rok Oman, Špela Videčnik, Janez Martinčič, Rok Dolinšek, Amadej Mravlak, Vladyslav Bondarenko, Adrien Riviere

technical team: Mizarstvo Ovsenik d.o.o.

contractors: Mizarstvo Ovsenik d.o.o.

landscape technology: MT Cvek d.o.o.

photographer: Miran Kambic | @mirankambic