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Fig. 76: Proposals (schematic) for various masonry elements

Examples from a Swiss manufacturer: "preton1 element catalogue

Fig. 76: Proposals (schematic) for various masonry elements

Examples from a Swiss manufacturer: "preton1 element catalogue

Rationalisation in the craftsman-like tradition

Factory prefabrication in the brickmaking industry has been driven in recent years primarily by economic considerations. The aim is to ensure that the traditional, time-consuming method of masonry construction, the nature of which consists of labour-intensive manual work on the building site, remains competitive with other methods of building. Apart from that, the quality of a masonry element has always been heavily dependent on the quality of workmanship and the weather. There are companies that can supply industrially prefabricated, custom-made masonry walls to suit individual projects. Such elements include reinforcement to cope with the stresses of transport to the building site and on-site handling by crane (e.g. "preton" elements), and can be ordered complete with all openings and slots for services etc.

This form of construction renders possible accurate scheduling of building operations, reduces the cost of erection and speeds up progress (making the whole procedure less susceptible to the vagaries of the weather). In addition, the components can be delivered without any construction moisture. On the other hand, they call for very precise advance planning and heavy lifting equipment on site. Another disadvantage is that there is little leeway for subsequent alterations, and none at all once the elements have arrived on site.

Such prefabricated masonry elements can be produced in different ways. One method is to construct them vertically from bricks and mortar (i.e. normally), but they can also be laid horizontally in a form, reinforced and provided with a concrete backing. Some bricks are produced with perforations for reinforcing bars. Furthermore, masonry handling plant has been developed in order to minimise the manual work in the factory.

It is also possible to combine conventional, in situ work with prefabricated elements; for example, the reveal to a circular opening, or an arched l intel - factory prefabricated - can be inserted into a wall built in the conventional manner.

On the whole it is reasonable to say that owing to the high cost of the detailed, manual jointing of masonry units to form a masonry bond such work can be replaced by erecting large-format, heavy, prefabricated masonry elements. Of course, the aim is to limit the variation between elements and to produce a large number of identical elements. Consequently, there is a high degree of standardisation. And a new problem arises: the horizontal and vertical joints between the prefabricated wall elements.

Fig. 77: Examples from a Swiss manufacturer: "preton" element catalogue

Masonry elements being erected at the Swisscom headquarters by Burkard, Meyer in Winterthur

Fig. 77: Examples from a Swiss manufacturer: "preton" element catalogue

Masonry elements being erected at the Swisscom headquarters by Burkard, Meyer in Winterthur

Fig. 78: Facade assembled from three different prefabricated elements

Burkard Meyer Partner: Swisscom headquarters Winterthur (CH), 1999

Fig. 78: Facade assembled from three different prefabricated elements

Burkard Meyer Partner: Swisscom headquarters Winterthur (CH), 1999

Two contemporary examples

Burkard, Meyer: Swisscom headquarters, Winterthur The entire facade of this building, completed in 1999, is a combination of three different standard elements, all of which were designed to match the building grid of 5.60 m. The three different elements are a) horizontal strip window with spandrel panel, b) plain wall, and c) double window. Apart from the peripheral concrete floor slab edges, all plain parts of the facade are in masonry. The wall elements of hard-fired bricks are reinforced and have continuous vertical grooves at the sides (see fig. 81). Inserting permanently elastic rubber gaskets into these grooves locks the individual wall panels together; that avoids the need for external silicone joints, which would be fully exposed to the weather. Each element is tied back to the I oadbearing structure at the top, and at the bottom fixed to the concrete nib with pins. All joints are 2 cm wide, and the horizontal ones remain open to guarantee air circulation behind the elements.

The wall elements comprise clay bricks measuring 24.4 x 11.5 x 5.2 cm which were specially produced for this project (optimum dimensions for corner details etc.). They were built in a jig manually in the factory. Besides the independence from weather conditions (construction time: 12 months indoors), the advantage of this for the site management was the fact that a standard element could be defined and it was then the responsibility of the factory management to maintain the quality of workmanship.

Right from the onset of design, the architects planned as many parts of the building as possible based on prefabricated elements. They also included the l oadbearing structure, which besides an i n situ concrete core consists of r einforced concrete columns, beams, and slabs (described in more detail in "Steel; Frames"). This is not heavyweight prefabrication in the style of panel construction, where the external wall elements are erected complete with loadbearing shell, thermal insulation, and internal finishes, but rather an additive combination of finished parts on site, i.e. a complementary system (see fig. 80).

In terms of the facade, reducing the number of standard facade elements to three and the fationalisation of the construction process through prefabrication was an advantageous decision in terms of logistics, engineering, and economics.

Swisscom headquarters: exploded axonometric view of facade

Fig. 79: Section through prefabricated facade element

Swisscom headquarters, Winterthur (CH)

Fig. 79: Section through prefabricated facade element

Swisscom headquarters, Winterthur (CH)

Fig. 81: Working (production) drawing for a prefabricated element

Swisscom headquarters, Winterthur

Fig. 82: West elevation, divided vertically into five segments: plinth, block, middle, tower, apex

Hans Kollhoff: high-rise block, Potsdamer Platz, Berlin (D), 1999

Fig. 82: West elevation, divided vertically into five segments: plinth, block, middle, tower, apex

Hans Kollhoff: high-rise block, Potsdamer Platz, Berlin (D), 1999

Hans Kollhoff: high-rise block:, Potsdamer Platz, Berlin The original plan was to construct a 100-m-high brick wall in Gothic bond. To do this, every bricklayer would have needed several stacks of bricks in various colours, plus specials, within reach on a 100-m-high scaffold. Owing to the load of the bricks, the hoists for the materials and the safety requirements, a very substantial, very expensive scaffold would have been needed for the entire duration of the project. In the light of the enormous size of the building and the complex logistics on the confined site in the centre of Berlin, the architects decided to use prefabricated components for the cladding. The industrially prefabricated facade elements were erected after the layer of i nsulation had been attached to the conventional loadbearing i n situ concrete frame. The windows were installed last.

Individual parts such as spandrel panels, column cladding, lesenes, and mullions make up the tectonic fabric of the f acade. Their depth and (partial) profiling result in a

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