Completed exterior of the Bossard project
quirements and nature of the building site and not of economy and efficien- cy, i.e. a different system of construc- tion might be employed to an entire- ly different project for a different client:
Total prefabrication is not always the answer.
These principles have led him to the following decisions:
Form, proportion, scale and depth of a building should be maintained in a precast concrete design:
A prefabricated building should not be temporary, and should look permanent and secure;
All joints of the elements should not be covered up with rendering but should be obvious;
The precast elements should not always be of smooth machine-finish but rather should be rough in order to express the character of concrete:
It is difficult to find a suitable site for a factory within a good radius for transporting the precast elements and therefore all the precast work should be done on the building site if pos- sible:
It is a waste of time to order extra elements from the factory right through the middle of a job:
The maximum size for the elements should be governed by the size of the cranes and the number of workmen available:
The construction of the main structure, whether in situ or precast, is often governed by the soil condi- tion and the shape of the building.
The system
Since the system is only designed for this project, the best way to un- derstand it is to study the project itself with the help of illustrations.
(a) Site lavout: It occupies 60,000 sq. metres of land sloping gently from north to south in a newly developed industrial area in Creteil. outside Paris. 500 dwellings have been built and divided into four types: two,
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three, four and five habitable rooms respectively.
They have been placed among 10 blocks of different sizes and slightly different shapes parallel to one an- other and at right-angles to the con- tours. The largest block consists of three different types of flats while the smallest one consists of two. A tower block and some other precast con- crete buildings designed by other people have also been built on the same site.
(b) Elements: In order to over- come the poor condition of the land and to achieve a more rigid structure, all the cross-walls and the outer por- tions of the floors have been built in situ (including the roofs). The inner portions of the floors are precast be- cause it has been found difficult to take off the shutterings from inside. The result is that all the precast elements have been tied together strongly by the in situ parts. (Ap- proximately 40 precast elements for each dwelling)
The precast elements consist of the following types: fascia-tie-beam units: flashing-tie-beams: floor-duct- tie-beam: wall panels: wall panel with window units: internal staircase units; vertical shafts; internal floor units: gargoyle units: ground floor external walls; and gutter-tie-beam units.
Wooden frames for sliding-win- dows were also made on the site and both the windows and precast ele- ments have been designed on a modular system based on the width and height of a cell.
Precast work was all done on the site by hands and fortunately the weather condition during the precast- ing period was good. Metal moulds were found too expensive for a job on this scale and therefore timber and concrete moulds were used. Ac- cording to the architect's design, a high degree of accuracy for precast- ing was not necessary.
(c) Planning:
Each block consists
Joints are left exposed of six storeys. The ground floor con- tains the entrance hall, storage areas. boiler room and tank room while the living area is on the floors above, Every two flats are served by one staircase: and all the flats have in- ternal staircases, bathrooms and kit- chens (except for the four-room type). All the windows are facing either east or west, except for the four-room flats which have south- windows.
Above each window is the floor- duct-tie-beam unit which also be- comes the support for a bench on the floor immediately above. Window- openings are of two types: complete window-opening and window-opening with precast panels, the back of which can be used as book shelves. For the bigger flats, some bedrooms can be divided into halves by sliding- doors.
It is interesting to compare the planning of this scheme to that of Coignet's. In this case, we have a more compact planning and a good variety of flats in which all the valu- able spaces have been given to living- rooms and bedrooms. In the other case, the planning seems to be forced on to satisfy the construction system and some valuable spaces have been occupied by staircases. bathrooms and kitchens.
However, the architect himself is not satisfied with a few points in his design. In order to satisfy some other requirements, some of the south-walls do not have window- openings: the internal staircases rely purely on artificial lighting: a better spacing of the blocks might have saved the number of cranes used.
(d) Erection: The best way to explain this is by sketches (see illustrations, page 61). The methods of joining the elements together are very similar to those in the Coignet System, except that in this case, the units have much more complicated shapes and therefore much more complicated joints.
Far East Architect & Builder May, 1965