Building envelope of Fritz Tower, Berlin

Trade Fair BAU ONLINE: Individually modelled ceramic tailor-made suit

The facade of the high-rise residential building designed by the architecture office Sauerbruch Hutton in the centre of Berlin sets design standards. It was planned with precisely calculated irregularity and conveys a thoroughly perceptible, pleasant presence. Glued to a thermal insulation composite system, it consists of only three ceramic elements from the "Craft" series of Agrob Buchtal: a threedimensional "V-pointed profile strip tile" in ochre-yellow and muted white as well as specially manufactured nosing tiles for the corners of the building. Apartment building as a landmark.

The new Lehrter Straße quarter is located just a few hundred metres north of Berlin's main railway station. It was developed over the last seven years on the basis of an urban master plan of the architecture office Sauerbruch Hutton and has transformed a former wasteland into a vital residential quarter with around 1,000 rented and owner-occupied flats. The architects developed a building structure consisting of six- and eight-storey individual buildings which zigzag along a railway line. Situated at the neighbourhood square with shops and pubs, the Fritz Tower marks the geographical and communal centre of the new quarter, which is visible from afar. The high-rise residential building with partly 8 and partly18 storeys houses a total of 266 micro-apartments measuring between 21 and 47 m². In addition, the building offers amenities such as e.g. a concierge service, a coworking space, an in-house gym and a public bistro.

A multi-faceted ceramic facade
The residential tower is unusual not only because of its furnished micro-apartments, which are rented out exclusively on a temporary basis, or its towering height. The eye is also caught by the ochre-yellow ceramic facade, whose unobtrusive sheen clearly sets it apart from the plaster facades of the neighbouring houses already from a distance. Anyone approaching the Fritz Tower from Lehrter Straße via the neighbourhood square experiences a slender high-rise building which rises evenly with windows elegantly routed around the corner and horizontal metal strips repeated every two storeys. "In pleasant contrast to this uniformity are the irregular light reflections which give the homogeneous building envelope an ever-changing appearance, depending on the viewpoint, the incidence of light and the time of day", explains Louisa Hutton, architect and co-founder of the Sauerbruch Hutton office.

The facade is also given a certain lightness by the many short white stripes which condense into long vertical lines in the plinth area and thus contribute to anchoring the high-rise building visually in the ground without any change of material. When you get closer to the building, the vertically arranged ceramic strip tiles of the "Craft" series of Agrob Buchtal become more and more visible - an effect which unfolds in a finely differentiated manner.

Functional and aesthetic
The architects decided on a glazed ceramic facade for three main reasons right from the start of the design phase of the Fritz Tower. "On the one hand, the material is robust, resistant and easy to clean - this is particularly important in high-rise construction, because it minimizes the number of maintenance and cleaning operations which can only be carried out under difficult conditions", says Vera Hartmann, the architect in charge of the project. "On the other hand, ceramics is a natural material that essentially consists of clay and conveys a homely warmth with its haptic surface qualities." The latter is particularly true of the strip tiles of the "Craft" series, whose glossy glaze reflects an astonishing depth and handcrafted manufacturing processes. The third reason for the ceramic strip tiles designed as V-pointed profiles is the comparatively cost-effective facade structure: the thin and light-weight elements form the ceramic "top layer" of a thermal insulation composite system which meets current energy requirements.

Minimum variety, maximum effect
Only two glaze colours (ochre-yellow and muted white) and two asymmetrical types of V-pointed profile strip tiles in two different dimensions (97 x 290 and 58 x 290 mm) were used on the facade surfaces. The individual rows run from bottom to top with equally aligned strip tiles, with their "noses" deliberately pointing either to the left or to the right. This combination alone creates a fascinating interplay of light and shadow as well as a distinctly three-dimensional facade. However, the architects wanted to go one step further and arranged the V-pointed profiles in a random pattern, thus creating a kind of irregular regularity. This irregularity, which is as informal as it is subtle, is in absolute harmony with a joint pattern which is perfectly coordinated with all the openings in the facade and the corners of the building. With great naturalness, the joints also refer exactly to the horizontal sheet metal strips structuring the facade every two storeys as a direct extension of the window sills. For architect Vera Hartmann, these metal sheets are by no means just design elements. "Rather, they interrupt the vertical rows of strip tiles and subtly create the possibility of making minor corrections to the joint pattern." In addition, they safely dissipate any moisture that could potentially arise behind the insulation layer.

Building corners to perfect the form
The building design of the Fritz Tower expresses an attitude which generates an image of loose irregularity and yet is based on extreme precision.This high conceptual standard is also reflected in the corners of the building. Their perfect formation was essential for the architects in order to make the ceramic covering appear as a homogeneous, tailor-made ceramic suit, rather than as a thin facade surface simply added on. It was therefore out of the question to simply butt the strip tiles together at the corners or to mitre-cut them and glue them together to form a corner profile. Instead, Agrob Buchtal developed in cooperation with Sauerbruch Hutton asymmetrical nosing tiles which matched the V-pointed profile strip tiles of the facade surfaces both dimensionally and aesthetically. These specially manufactured ceramic special pieces act as a link and ensure consistent materiality - unlike, for example, corner profiles made of metal. In order to optimally implement the design ideas, the ochre-yellow basic facade colour was also developed according to the architects' ideas. For determining the appropriate glaze colour, workshops were held in the Agrob Buchtal glaze laboratory, where more than 16,000 different recipes for project-specific individual glazes have been created to date. These workshops resulted in several samples and test areas. In the end, Sauerbruch Hutton succeeded in translating the client's wish for a shiny golden facade into a solution which is elegant, durable and of high quality even without any direct reference to this precious metal.

www.sauerbruchhutton.de

Contact
Werner Ziegelmeier (Head of Public Relations)
Phone: +49 (0)9435 391-3379
Mobile: +49 (0)160 90527159
Fax: +49 (0)9435 391-303379
Email: werner.ziegelmeier@deutsche-steinzeug.de

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Source: Agrob Buchtal GmbH / Jochen Stüber

Motif 1

The new Fritz Tower marks the geographical and communal centre of the new Lehrter Straße quarter in Berlin, visible from afar on the neighbourhood square with shops and pubs.
Source: Agrob Buchtal GmbH / Jochen Stüber

Motif 2

The building envelope consists of only three different ceramic elements from Agrob Buchtal's "Craft" series: three-dimensional "V-pointed profile strip tiles" in two shades (ochre-yellow and muted white) as well as nosing tiles specially produced for the building corners.
Source: Agrob Buchtal GmbH / Jochen Stüber

Motif 3

Ceramic nosing tiles specially manufactured by Agrob Buchtal enable technically and visually stringent corner solutions which lend the building envelope sovereign homogeneity.
Source: Agrob Buchtal GmbH / Jochen Stüber

Motif 4

Irregular light reflections ensure that the building envelope is extremely multi-faceted and always appears different, depending on the viewpoint, the incidence of light and the time of day.
Source: Agrob Buchtal GmbH / Jochen Stüber

Motif 5

The sheet metal strips, designed as a direct extension of the window sills, provide a structuring of the facade to scale and rhythmize the vertical rows of strip tiles.
Source: Agrob Buchtal GmbH / Jochen Stüber

Motif 6

Short white stripes give the facade a certain lightness. In the plinth area, they condense into long vertical lines which visually anchor the high-rise building to the ground without any change of material. All the joints are perfectly coordinated with the facade openings.
Source: Agrob Buchtal GmbH / Jochen Stüber

Motif 7

The individual rows run from bottom to top with equally aligned strip tiles, with their "noses" deliberately pointing either to the left or to the right. In addition, the V-pointed profiles are arranged in a random pattern, thus creating a kind of irregular regularity as well as a fascinating play of light and shadow.