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Montessori Children’s House and Primary School Arusha Region, Tanzania

Competition 1st Prize

In collaboration with APC Architects, Annika Seifert, Wolfgang Rossbauer

Wood Joints 

Expression of Tectonic Culture

Wood joints reflect the different building cultures in timber construction. They are shaped by climate and material, but also by aesthetic values.

An exhibition of the material collection in the Department of Architecture at ETH Zurich shows traditional, pure wood connections from Europe and the Anglo-Saxon area, as well as from China and Japan. It also shows how wood joints are used in current and future construction projects. 

Material Hub ETH Zurich

Department of Architecture                       

Exhibition: 10 May 2019 – 5 September 2019

Opening: 9 May 2019, 18.00 hrs

Flying beams

Lever rod bridges in China

With lever bar systems, considerable spans can be achieved with short components. The curved construction is self-reinforcing, the system replaces joining to a certain extent, connections are reduced to a minimum. In China the more than 1000 year old technology is experiencing a revival, in Europe Leonardo Da Vinci’s designs are finding interest again.

Article in the Swiss architectural magazine

werk, bauen+wohnen. May 2019
Fügen in Holz

Bienal de Arquitectura Quito, Ecuador 2018

Swiss timber construction between tradition and innovation

The building material wood has experienced an impressive renaissance in the last decades in Switzerland and also internationally. Above all, rapid technological development and growing ecological awareness have turned this traditional material into a sustainable building material of the future with great potential. On the one hand, timber construction is gaining in importance in Switzerland due to its energy and cost efficiency, especially in cities. On the other hand, research and further development ensure an exciting interaction between traditional, proven technologies and increasingly efficient industrial and digital technologies. Current examples are used to discuss this development and provide an outlook for the future.

Article in the Chinese architectural magazine The Architect . 193, June 2018

IN LAND   AUS LAND  Swiss Architects Abroad

The promenade roof of the Mkombozi School in Chamazi, Dar Es Salaam, Tanzania has been selected for the exhibition IN LAND   AUS LAND held in the Swiss Architecture Museum in Basel.

01.07. – 12.11.2017

Exhibition Positionen

M:AI Museum für Architektur und Ingenieurbaukunst Gelsenkirchen

Oct. – Dec. 2015

From various joint works and the spatial office community with BHSF Architects, a joint exhibition contribution developed in 2015 in the M:AI, the Museum for Architecture and Engineering Art NRW. Five Swiss offices were invited to develop a joint exhibition installation in Gelsenkirchen’s StadtBauRaum. The exhibition should create a visible framework for discussions and promote direct exchange between visitors and architects. The exhibition contribution, a reciprocal framework work made of cardboard tubes connected with hemp ropes, was erected with the support of students from the TU Cologne and reused in another form after the exhibition within the framework of Passagen Köln 2016.


Residence of the Swiss Ambassador Port-au-Prince Haiti

Complete Refurbishment and Interior Design, 2011-2013

The residence of the Swiss Embassy in Port-au-Prince,  was damaged by a severe earthquake in 2010. The overall refurbishment essentially comprised the reconstruction of the house, the renewal of the technical and security infrastructure, rehabilitation measures to ensure earthquake safety, the landscape design and new furniture in the representative areas and interior design.

Project by Thoennissen + Precht Architecture and Urban Planning

Residence of the Swiss General Consul São Paulo

Interior Design, 2015-2017

In the course of the reconstruction and renovation of the residence of the Swiss Consul General in São Paulo, the representative rooms and the outdoor areas were refurbished. The residence building dates from the 1950s and is characterised by its clear, modernist design. It evolves around a U-shaped garden courtyard.

The furnishing concept sees a mixture of Brazilian and Swiss furniture from the 50s and the contemporary period, which with their organic, handcrafted forms set a counterpoint to the clean lines of the house.

In the outside area a tile cladding was applied by the Brazilian artist Alexandre Mancini. For the interiors, works by the Zurich Concretists around Max Bill were mainly chosen.

Architecture, furniture and art thus merge to form a unity. 

© images: Nelson Kon

Residence of the Swiss Ambassador, Brasilia, Brazil

Interior Design, 2016 – 2017

House Eagle

Renovation and conversion, 2016-2018

The renovation of this house from 1939 focused on the typology and the existing substance of the building. The house is part of an ensemble of four houses in Zollikon, all positioned gabled in a slope.

In the interior, the open, staggered room sequences and views were restored. The outer cubature was reconstructed to its original form. Only the roof was raised and equipped with four large dormers.

In collaboration with BHSF Architects.

Residence of the Swiss Ambassador in Quito, Ecuador

Renovation and conversion, 2017-2019

The house is one of the most important buildings of the post-war modernism in Ecuador and was built in the year 1972 by the famous architect and artist Oswaldo Muñoz Mariño for himself and his family. 

As part of the overall refurbishment, the residence has been modernized, rebuilt and earthquake-proofed. 

The house consists of two parts, each of which has different room types and functions. The public part in the west is a modernistic building with a large saddle roof. In the east this includes a single-storey building with masonry domes and -vaults around an inner courtyard.

In collaboration with arquitectura X, Quito.

Mkombozi Promenade Roof

Chamazi, Dar Es Salaam, Tanzania, 2016 – 2018

The covered promenade forms the backbone of the Mkombozi Primary School, a church-owned primary school in Dar es Salaam, Tanzania. Not only does it connect the various school buildings and outdoor areas, it also offers space for a variety of activities such as lessons, games during breaks and lunch.

A construction was sought that would provide sufficient ventilation in the courtyards even after the extension by further school buildings. 

The substructure of the vault is made of steel for structural reasons and to protect against termites. The irregular distances between the columns react to the class wings, which are alternately lined up on both sides of the promenade and interrupted by planted courtyards.

The vault itself forms a wooden reciprocal framework. This kind of structure is suitable in areas where highly developed carpentry techniques and engineering timber are too expensive, and where long timber lengths are difficult to obtain for transport reasons. The construction principle was used thousands of years ago, and in recent years ETH Zurich has been researching solutions for its use in current construction. The findings of this work have been incorporated into the roof.

In collaboration with APC, Dar Es Salaam.

research & teaching

Reciprocal Structures

Reciprocal structures are known to builders since time immemorial and they can be regarded as a universal principle of construction. In history they have been used to efficiently bridge large spans deploying short wooden elements. They were additionally attractive for buildings where rapid assembly and dismantling was required, and where geographical circumstances impeded the use and transportation of longer construction elements. In many treatises medieval and renaissance architects, mathematicians and builders like Leonardo da Vinci studied the possibilities of these structures. Because of the complex structural behaviour, however, there has been only very limited number of applications in architecture to the present.


A digital design tool developed at Federal Institute of Technology Zurich enhances the design scope and the application potential of reciprocal frame systems. It is intended to make the use of simple wooden elements in buildings more attractive, above all in lower-cost free structural forms. It offers a unique completely new aesthetics which combines ancient knowledge and innovative technology. Nearly all vaulted and flat forms are possible, in a lot of available materials.

Canopy in the ETH entrance courtyard

This RF construction is made of a squared timber type and the simplest of joints. The design was undertaken exclusively using the digital instrument, whereas production was undertaken manually. The specific arrangement of the timbers in different lengths produces a differentiated structure in which the interdependencies of structure and form are immediately intelligible.

Pergola  ETH Science City

This pergola for the ETH Zurich campus was initially designed using the digital instrument and statically optimized during the design process using physical and digital models. The one-of a- kind elements were then cut from wooden boards using a 3-axis CNC milling machine.

Villa Hatt Canopy

In this pergola for the ETH guesthouse an inner reciprocal frame lattice is enhanced on the principle of the Leonardo-da-Vinci bridge. The material is hardwood, the production was done by conventional a joinery machine.

Saddle Roof

As a rule in reciprocal frameworks the circumstance that all of the elements rest mutually on each other produces convexly curved forms, such as domes and arches for example. However, comparatively regular mesh designs in which the slats follow the lines of curvature can – when the lines are given a particular alignment – also result in concavely curved surfaces, in this case a saddle surface.

Super Dome Ifakara Tanzania

In summer 2016 a summer school of the HSLU Lucerne took place in Ifakara, Tanzania. This design-build-workshop dealt with the use of found materials and techniques and took place for the third time at the same location. For two weeks, students from Switzerland and Tanzania came together and, with the support of local craftsmen, built a roofed workshop that will also serve as a festival hall and meeting place for the neighborhood. Here, a reciprocal framework made of round teak logs was used, which spans the square ground plan in concentric rings and forms a flat dome shape. Above this wooden dome floats the actual roof, which ensures good ventilation via a secondary construction and thus reduces the thermal radiation of the sheet metal roof to the inside.

FAAP São Paulo Zollinger Roof

The workshop is part of the first postgraduate program for architects in Brazil with a focus on timber construction. During 10 days, a temporary lamella construction was developed to serve as a place for exhibitions and teaching. It stands in the entrance area of the FAAP in the elegant district Higienopolis and mediates between the sculpture garden and the main building, which was built in 1956 by Auguste Perret.

The basic component of the lamella structure, also called Zollinger roof, is a lamella with the dimensions 200x20x4cm made of eucalyptus wood. The barrel-shaped structure consists of 270 lamellas, which were processed with a Hundegger joinery machine and by hand. 

The load-bearing rhombic structure will be covered with wooden slats that protect the interior from the sun.

Visiting Professorship 

Nanjing University, China



            Runner up

Reciprocal Frameworks – Tradition and Innovation

The fascination of reciprocal frameworks lies in the effortlessness and lightness of their seemingly interwoven elements. The diversity of the forms and patterns of these constructions are created by an interaction of mutually supporting members – a technique already exploited by master builders hundreds of years ago.

The book examines the history of this load­-bearing principle right up to current architectural practice and provides examples of how it is possible using digital tools to expand the current applicational fields of reciprocal frameworks.

2015, 22.5 x 25.5 cm, 232 pages, 234 ill.
gta Publishers Zurich
ISBN 978-3-85676-344-2


Udo Thönnissen practices as an architect and designer in Zurich. He studied architecture at the RWTH in Aachen and the UIC in Barcelona. Besides his professional activities his special interest lies in reciprocal structures.

He has been a lecturer and researcher at the ETH Zurich. He has published various contributions in journals and books and has headed workshops at numerous architectural faculties in relation to research into reciprocal structures.


Udo Thönnissen

Via Costa di Fuori 7
6614 Brissago

Hardstrasse 69
8004 Zürich