Vertical span




            In Europe, after a strong overcome
of the concrete in the 20th century as the primary construction material,
combined by the movements of Modernism and Postmodernism, the traditional
construction materials, such as stone, wood or brick were held back by the
speed of building process during the last century.

            Before this period, some regions
from all over Europe, had a significant connection with their own land, and
this was shown also by their architecture. There wasn’t a universal building
technology, which everybody can acces it, neither the preparation of the local
masterbuilders was not enough for a wider use of material. It is well known, that
the vernacular architeture (architecture without an architect) uses the possibilities
offered by its own land and forms its own people. If we look at the older
buildings, the historic centres of the settlements or at the wider landscape,
by studying them, we can have a really precise knowledge about how the land
forms its own habitants and how they do habit their space. This observation, if
we apply all over the continent, dividing in time during the centuries, we can
easily classify smaller or bigger communities, regions, or even states, which
share a common building technology, material or technique given by its
territory. As examples, we can mention the stone architecture of Ticino, in France,
the wood architecture from Norway, Switzerland, Austria, Transylvania or the brick
constructions of the Romans and Greeks.

            Universally, all these heritage of
the past was put away in the last century, giving place of the era of the
concrete. Interestingly, some local regions, still remained in contact with
their own architectural heritage, without needed to deny their local inspiration.

In Switzerland, one of the most significant area where the local architecture
had a continous history and evolution was the canton of Grisons. This area of
Swtizerland, was always characterized by wood constructions, which we can
translate with the landscape of forests through the whole area. There is a
significant heritage of log constructions, called “Strickbau” or
“Mischbauweise”. This region, in the 20th century, when the concrete
as material was having his paradise, gave birth to some significant specialists
in the field of construction, or was the place where they performed in their
highest level. The canton of Grisons became a pilgrimage land for architects
and specialists, interested in wood constructions. There is a rational and
pragmatic world which appears in the front of the visitor, helped by strong
engineering condition, which gave birth of significant projects. Also, this
attiude has its positive and negative aspects. Thinking of the fastly grown
infrastructure, highways, bridges, office buildings, without any substantial
preoocupation to the details, the projects you can find in Grisons, are a deep
knowledge about the place, the people, the material itself, and this results in
a simplest architectural structures, solved even the very last detail in a
unique level, which as Peter Zumthor once confirmed: “I think you have
bigger chance to find beauty, if you are not working directly on this. The
beauty in architecture is held by its expedience. This is, what we can learn
from the city- and villagescapes built by the Swiss farmers. If you do what you
need to, then in the end will result in something, which maybe you cannot
explain, but if you are lucky, it is linked directly to the life.”


            As having this as starting point, it
was interesting to study how in contemporary architecture form Grisons is the
wood still applied. Luckily, during the last period, some significant
architects and engineers did work with this material and they did contribute to
the evolution of the building technology of the region. Among other, less well
known professionals, the works of Peter Zumthor, Bearth & Deplazes, Gion
Caminada or Hans Jörg Ruch are the most important to mention.

            For this work, were selected four
projects, each of them from a different architect, but by the same engineer,
Jürg Conzett. All the works are built in Grisons, all by local architects and
all of them treat the theme of the span, of an opening over a wider empty space,
with a careful and unique architectural and static design, all made in wood. All
of the studied situations, treat the same problem in a different way, the
functions of the buldings is also diverse.


            The selected works are:

School Gymnasium in Flerden by
Hans Marugg

Multipurpose Hall in Alvaschagn by
Bearth & Deplazes

Verweilbrücke in Trutg dil Flem by
Jürg Conzett

Community Hall in Vrin by Gion


            The purpose of this confrontation is
to have a deeper image in the understanding of how a simple question, of a
span, can be solved in different ways, having the same cultural basis.





Gymnasium, Hans Marugg, Flerden, 1992


            One of the first project on which
the newly established office of Conzett started to work, was the School building
in Flerden, designed by Hans Marugg, an architect form Engadin. Being a school
building, the opening to cover with the roof was about c. 12m in its width. The
used material was glulam timber.

            The starting structural principle of
the roof of the gymnasium was abstract, to use the laminated timber as
two-dimensional elements, in order to apply as a concrete based wall-slab
system. The initial idea was to have a single ridge beam structure with a
central purlin, as is well suited for the simple shape of the roof. Due to its
opening, in this case the beams would have act as simple beams, having too big
bending moments. The sections of the elements, would need to be overly large.

            For economical reasons, a variant of
the above design was applied, having two central purlins. The bending moments
of these are reduced, complemented by small cantilevers at their end.

            All the pieces are the same
thickness, 100mm, and are designed as walls or slabs, so in section, they look
like shallow rectangles. The orientation of them are decided by the structural
roles they have, as: the lowest tension piece of the frame is orientated
horizontally in his plane, in order to overcome the orizontal forces generated
by the hung sports equipment. This piece is in the middle is almost two times
wider than its ends, where also is a one and a hal meter long cut, for the
linking purlins. These purlins are orientated upwards, as the diagonal struts
to take over the bending forces. The purlins have a specific geometry, while
the struts have the same principle as the flat piece, two times wider one end
than the other. These struts, are linked together by a short, approximately 2m
long horizontal compression beam, also orientated upwards. Between the struts,
we can find two diagonal joists, also increasing in size upwards, where they
connect the struts. These elements are not completely vertical, they have an
inclination of 9 degrees, this angle being the bisector of the inclination of
the two type of struts. These struts, while are sandwiched by the compression
struts, at their side, they also hold the bigger part of the roof. For this are
provided two 25cm wide “moustaches” on the pieces, on which are
standing the beams of the roof, orintated perpendicular to the orientation of
the fall of the water. As the struts overtake the forces, they transfer them to
the horizontal tension piece, which transfers them at its base.

            At the both of the basis, are
birch-ply pieces, having a unique designed shape, which resist the shear
stresses. Through the whole roof system, beside glueing, there are visible
construction screws for a better connection between the elements.

            By this system, for the whole roof
structure over the gym, were used just 40 elements. Six pieces by each pair of span,
and other 10 for the longitudinal roof beams.



Hall, Bearth & Deplazes, Alvaschagn, 1990-91


principle of overlayed structural systems were often used in the preindustrial
era. Maybe the most famous example for this is the bridge of Hans Ulrich
Grubenmann form Schaffhausen from 1758. The advantage of the structural overlay
consists in principle of solidarity: while one system stop working, then
another system comes into the scene, helps, and all together resolves the

            This is the
case of the village hall from Alvaschagn, designed by the architecture office
Bearth & Deplazes. The function of the building is a multipurpose hall,
deserving as space for cultural and community events, but also for sport
activities. The use of the space needed and adaptable structure, so there you
can store the sport equipment away during the concerts or plays.

            The main
load fo the roof structure comes form the snow. As the biggest shear forces
appear in the horizontal pieces, before they are transferred to the sides; the
sides, as being the smallest part in section of the roof, due to the roof
geometry, need the bigger number of noggins.

            The whole
system can be divided in three portions. All three portions are enclosed by
laminated timer profiles, shaping the silhouette of the frames. The middle
piece is 220mm wide and and inside the frame, There is a stiffened arch of thin
laminated timber. This arch is taking over most of the vertical forces of the
roof. On the side of this frame, there are attached 27mm thick plywood plates
in order to take over the forces form the snow. The combiantion of this system
provides a thin construction. In addition, against the shearing forces, are
added two more frames on both sides, creating a box construction together with
the plywood plates. Through all the construction, the horizontal pieces are
much thicker than the vertical ones. The explanation of this means that the
moments on the corners are smaller under the vertical loads, the horizontal we
can be considered as simple beams, and verticals are acting when horizontal are
applied, against the lateral bending moments.

            In the
construction technology, this meant that the corner pieces are simply the fixed
starting elements, and to this were stiffened the other pieces by gauge bolts. As
the arch is inside the “sandwich” construction, just the bolts on the
plywood plates hint its existence.

            The whole
construction is fixed together with bolts on horizontal, and later on were put
in place all together. As the frame is getting shallowers as going downwards to
the ground, the section at its very lowest point arrives to approx. 200x500mm
massive timber.

combination of the conctruction system, arch and boxes, underlines the
efficiency of the combination, as each system takes over the loads of which was
originally intended to be: the thin boxes as load-distributor, while the arch
as good stifness under a uniform load.



Community Hall, Gion Caminada, Vrin, 1995


building is one of the most significant among Gion Caminada’s career and it was
important for the architect’s fame in his own region and village. The theme of
a community hall was nothing expectional in the canton of Grisons, some of the
renoowned local architects had the chance to complete one.

such as Vrin has very few communal spaces, beside the school, just the church
could be considered that. In addition to these was commisioned Gion Caminada by
the local authorities, to complement the coherent appearance of the church and
the school built in 1857. As most of these community halls, the space also
needed to serve as a gym for the neighbouring school. Given the theme, were two
important factors in his design, which we cannot find in the above two
examples. The village of Vrin is on a big slope, and such a big footprint
hardly can find its place flat. The second was an incredible connection of the
architect with the building material and the conservation of the Alpine
territories; he is saying that the goverment should protect the farmers, as
they are the guardians of the Swiss Alpine landscape.

these two aspects, the bulding is a wooden roof on a concrete plinth.

Positioned dramatically on the edge of the village, where the slope starts to
head down, there was buitl a solid concrete plinth, half in the ground (facing
upwards the hill). The timber also refelcts the richness in pine of the
community, but also the local architectural tradition. Using local timber, cut
at the nearby sawmill, there was a possibility to obtain large cross sectioned
wood pieces. The opening to cover was about 11m wide, and for this, it was
possible to use these huge pieces of wood as non-spliced tension members. The
orientation and arrangment of the fibers was also a help, so like this, the imagined
structure was like a very simple open girder construction, the single challenge
being in the connection of the ends of the beams. Other contemporary strcutres,
for which glulam timber was used, supposed to be cut and assembled in the
workshop, providing a big precision and accuracy of the result. Not in this
case, where the frames were built on the site, and the connections were added
later. The massive timber elements are useful in traction, and the idea was to
be joined with flexible nodes.

            During the
design process, Conzett used as a reference the Magazzini Generali SA building
in Chiasso designed by the renowned Swiss engineer, Robert Maillart. This
reference was considered during the process, as the the initial two beams structure
had a strctural problem for which Maillart provided a solution.

difference between Maillart’s and Conzett’s design, was that in Chiasso, the
roof is tensioned just by a think skin of snow, while in Vrin, this wood roof
structure needs to resist to heavy snow loads and strong open winds, as is
positioned on an open edge of a slope in a valley. This also means that in
Chiasso, the snow is mostly uniformly distributed, but in Vrin is significantly
assymetrical. At this point, other refernces were considered by Conzett, the
Bridge near Donath and the one near Tamins, both made by Maillart.

            The central
joint between the two beams was tempted to move upwards as the compression
forces act in their end, so there was no need for a central vertical support.

In contrast, the ends of the beams are tempted to act
outwards, so a bottom chord was introduced. This chord is made out of five 25mm
thich timber planks, going through the whole space creating an almost constant
curve under the roof beams. The interesting part of the structure is the joint
between all these elements. Needed to be found a system which allows to connect
each plank individually to the beams so they can act as a chord. For this, were
used thin steel plates. Every of these plates were holed in the middle, with
the thickness of the beams, folded in two, slunged around horizontally over a
24mm diameter dowel botls. The two ends of the steel plates were holed each
with 4.5mm holes, each of them having 84 holes. It was necessary to have a
strong connection spread in as much screws as possible, cinsidering the small
thickness of the planks. These plates are clearly using the principle of a tension

            A delicate
part of the structure is the laterial connections. Based on the principle of
the bridges by Maillart, as the loads from the beams are directioned downwards,
bigger and bigger compression forces are appearing. As the middle could be
open, considering the pushing upwards, the other ends needed to be anchored, to
reduce the moment variants. There were introduced 12 pieces of vertical
elements. Each of them is growing in its transversal section as it goes more to
the lower end of the roof. The short distance between these elements also prevents
the planks from buckling.

            The design
of the roof is interesting as it stoods out of its predecessors made by
Maillart, converting them into a high-performance hybrid system, but still do
not deny neither the local architectural traditions, nor the experience of
creating something new.



Verweilbrücke, Jürg Conzett, Trutg dil Flem, 2010





99. Conclusion


100. Bibliography


101. Certificate of originality

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