The school implies the materialization of the reflection about the role
that wood construction plays in modern
architecture.
Not only manufacture and assembly new processes are experimented in this
project, but also a new approach to the application of this material.
The school raises at the outskirts of the Swiss city of Biel-Bienne ( approximately
40 km away from Bern), in a bordering area of Jura mountain range.
This project opens a new field of research: the use of wood as a basic
construction material to build up a big public building and the possibility of
its existence in an urban context.
The building forms part of the enlargement of the ancient school and
integrates some pre-existing edifications.
The proportions and dimensions of this building do not correspond to the
traditional and preconceived image of a wood construction; that familiar
picture which, by contrast, we recognize immediately in the surrounding
landscape.
Among this traditional constructions the schools big mass presents a
curious classic aspect= cornice, main body and a plinth underlined by a shadow
line.
The volume of the school is contained in a big parallelepiped of 94m
length, 24m width and 17m height.
The irregular interior distribution does not match with a rigid
geometry. Alongside the central corridor arise always changing views.
With a nearly identical distribution, the three first floors contain the
different classrooms.
Last floor, which is arranged
with more flexibility, is occupied by the administration and by the offices.
Everything seems to be out of scale, the elements seem child
construction game pieces: the big spans, the oversized openings, the giant
columns and beams that hold up the roof... the sensation is also felt inside,
in the big 11m height wood box that sets up the hall, with its disproportionate
radiators and the enormous lighting screens.
Big oak panels organize the façade with horizontal and vertical bands.
In contrast to which is habitual in wood construction, in this case
structure performance does not remain hidden behind the cover.
Inside, the truthful leit-motiv is the contrast: disproportionately big
doors opposite to excessively low passages.
The concrete central spine acts as a evacuation route in case of fire.
It is a monolithic whole with big cantilevers (possibly due to the gradual post-tensed
of slabs, structurally independent to the attached wooden big boxes).
The centerpiece is a monolithic structure with an almost sculptural character.
The slabs rest on concrete boxes that house vertical circulations and wet areas.
They are placed staggered so that, alongside with the irregular arrangement of
the terraces, break the monotony of the corridor scheme and force you to follow
a zigzag path.
Post-tensioning allowed to suppress expansion joints and to build large
overhangs, which have only to support themselves. The post-tensioned of the foundation
slab was developed in several phases. Both the concrete core and wooden boxes
sit on precast piles, as the solid ground is more than five meters down the
surface.
The color takes part in the construction of the space. In the
stairwells, yellow enhances the effect of the light running down the wall,
while the dark grey emphasizes the differential functioning of the top floor. Bluish
gray is applied on the underside of terraces slabs and in the concrete ,
accentuating the visual relationship between the inside and the outside.
In the project coexist two independent structural patterns associated
with the use of two basic materials that complement each other: wood and
concrete.
The biggest challenge was to overcome the limits of the rules imposed by
the normative of security against fire. This challenge was even greater because
architects proposed a building of four storeys. This problem was approached
with not only technical but also architectural measures: the long block was
divided into independent boxes attached to both sides of a concrete core that
works as an escape route.
Starting from the north side, the boxes were lifted one by one, mounting
them completely due to their self-supporting capacity.
Floors
(A) - wooden alveolar plates - rest provisionally on the beams which in turn rest
on either the basement wall, or right over the heads of the piles and an
intermediate auxiliary peg.
The
corners of the plates (B) are cut, so that the pillars are supported directly by
the concrete piles.
On the
floors perimeter elements are placed. The wall that faces the hallway, a
classic framework (C), covers two modules width and is stiffened with
wood-cement boards (D).
The six
wooden "boxes" are structurally independent and self-supporting. These
contain the classrooms, which volume is adjusted to the structural module, being
in this way treated as individual units.
The
walls that close each of the boxes are load-bearing walls. The interior slabs
rest on the facade slabs and on those which close the hallways, while the lateral
slabs support the terraces. The interior partitions dividing the modules are
not load-bearing, so that they can be placed according to the size required for
each room. Front walls do not work as a lintel system but as perforated panels where
all the elements work.
The
intention was to eliminate the need for partitions in windows, but without
increasing the lintels thickness- this corresponds to the minimum required by
the requirements of fire protection - so that it could not impede the entry of
light into the classrooms.
Facade
elements (E) act as perforated panels, from which floors are hung once are
situated in the perimeter.
The lateral
walls of the first floor (G) support the terraces and the enclosure of the
upper floors.
The
facade is a structural surface in which all the parts are working. It is constructed by prefabricated components
of two modules width covering the height of a floor.
Once the
next slab is arranged (B), the ring corresponding to the new floor is
constructed. The side walls (C), as they have not to support heavy loads, are
from the second floor simple frameworks.
Large
eaves unify different elements below. They are merely a formal game, or maybe a
very important part of a design aimed to protect the wood, because they reduce
the action of atmospheric agents on the facade. The north wall is totally
blind.
Boards that
cover walls are formed by a frame (A) and several untreated oak tables (B),
reinforced with dovetailed wedges (C).
They are laterally screwed to the structure with folded sheets (D) fixed to the
frame.
The
basic skeleton of the deck is solved with porches formed by big box beams.
In the
floor, an acoustic insulation and a sand base, avoid contact points between
pavement and structure, eliminating the transmission of impact noise.
The
wooden structure is self-supporting and never rests on the concrete structure.
The gap left between the timber frame and concrete slab is used for housing installations.
The
impressive space of the lobby, which occupies the north wall, has a height
equivalent to three floors and communicates directly with the old dining room,
preserved as an attachment of the new building. Its facades, covered of pine
wood, contribute to the feeling of being inside a box of a disproportionate
size. In the absence of slabs or other lateral elements, the wood covering
based in wooden panels stabilizes the walls.
